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	$205.72	3.223%	$212.3504	$212.35	$212.35	$212.40
Purchase #2	$129.25	11.138%	$143.6459	$143.65	$143.65	$143.60
Purchase #3	$65.71	9.237%	$71.7796	$71.78	$71.80	$71.80
Purchase #4	$155.90	13.351%	$176.7142	$176.71	$176.70	$176.70
Purchase #5	$159.29	3.191%	$164.3729	$164.37	$164.35	$164.40
Purchase #6	$85.90	5.813%	$90.8934	$90.89	$90.90	$90.90
Purchase #7	$80.40	5.673%	$84.9611	$84.96	$84.95	$85.00
7 purchase totals =	$882.17		$944.7175	$944.71	$944.70	$944.80