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	$85.92	9.234%	$93.8539	$93.85	$93.85	$93.90
Purchase #2	$7.34	7.868%	$7.9175	$7.92	$7.90	$7.90
Purchase #3	$140.61	8.479%	$152.5323	$152.53	$152.55	$152.50
Purchase #4	$216.26	3.366%	$223.5393	$223.54	$223.55	$223.50
Purchase #5	$184.46	13.151%	$208.7183	$208.72	$208.70	$208.70
Purchase #6	$87.90	5.381%	$92.6299	$92.63	$92.65	$92.60
Purchase #7	$72.85	11.338%	$81.1097	$81.11	$81.10	$81.10
7 purchase totals =	$795.34		$860.3009	$860.30	$860.30	$860.20