Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $183.57   9.599%   $201.1909   $201.19   $201.20   $201.20  
  Purchase #2 $140.25   9.234%   $153.2007   $153.20   $153.20   $153.20  
  Purchase #3 $156.30   6.111%   $165.8515   $165.85   $165.85   $165.90  
  Purchase #4 $42.41   8.317%   $45.9372   $45.94   $45.95   $45.90  
  Purchase #5 $141.77   10.376%   $156.4801   $156.48   $156.50   $156.50  
  Purchase #6 $72.26   5.370%   $76.1404   $76.14   $76.15   $76.10  
  Purchase #7 $158.61   3.317%   $163.8711   $163.87   $163.85   $163.90  
  7 purchase totals = $895.17       $962.6719   $962.67   $962.70   $962.70