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	$153.85	10.590%	$170.1427	$170.14	$170.15	$170.10
Purchase #2	$125.29	12.432%	$140.8661	$140.87	$140.85	$140.90
Purchase #3	$69.92	9.110%	$76.2897	$76.29	$76.30	$76.30
Purchase #4	$64.26	10.364%	$70.9199	$70.92	$70.90	$70.90
Purchase #5	$234.28	13.316%	$265.4767	$265.48	$265.50	$265.50
Purchase #6	$159.56	12.460%	$179.4412	$179.44	$179.45	$179.40
Purchase #7	$99.90	11.146%	$111.0349	$111.03	$111.05	$111.00
7 purchase totals =	$907.06		$1,014.1712	$1,014.17	$1,014.20	$1,014.10