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	$221.82	10.353%	$244.785	$244.79	$244.80	$244.80
Purchase #2	$79.89	3.764%	$82.8971	$82.90	$82.90	$82.90
Purchase #3	$149.36	8.210%	$161.6225	$161.62	$161.60	$161.60
Purchase #4	$5.77	9.390%	$6.3118	$6.31	$6.30	$6.30
Purchase #5	$54.69	11.846%	$61.1686	$61.17	$61.15	$61.20
Purchase #6	$124.95	11.729%	$139.6054	$139.61	$139.60	$139.60
Purchase #7	$229.83	7.680%	$247.4809	$247.48	$247.50	$247.50
7 purchase totals =	$866.31		$943.8713	$943.88	$943.85	$943.90