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 $94.29   4.266%   $98.3124   $98.31   $98.30   $98.30  
  Purchase #2 $208.71   11.153%   $231.9874   $231.99   $232.00   $232.00  
  Purchase #3 $85.52   11.113%   $95.0238   $95.02   $95.00   $95.00  
  Purchase #4 $87.76   4.494%   $91.7039   $91.70   $91.70   $91.70  
  Purchase #5 $208.76   3.609%   $216.2941   $216.29   $216.30   $216.30  
  Purchase #6 $85.35   3.154%   $88.0419   $88.04   $88.05   $88.00  
  Purchase #7 $181.60   7.850%   $195.8556   $195.86   $195.85   $195.90  
  7 purchase totals = $951.99       $1,017.2191   $1,017.21   $1,017.20   $1,017.20