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	$179.41	9.571%	$196.5813	$196.58	$196.60	$196.60
Purchase #2	$27.34	7.683%	$29.4405	$29.44	$29.45	$29.40
Purchase #3	$162.40	4.848%	$170.2732	$170.27	$170.25	$170.30
Purchase #4	$124.48	5.325%	$131.1086	$131.11	$131.10	$131.10
Purchase #5	$181.71	5.733%	$192.1274	$192.13	$192.15	$192.10
Purchase #6	$106.66	9.231%	$116.5058	$116.51	$116.50	$116.50
Purchase #7	$54.26	13.250%	$61.4495	$61.45	$61.45	$61.40
7 purchase totals =	$836.26		$897.4863	$897.49	$897.50	$897.40