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	$43.86	5.500%	$46.2723	$46.27	$46.25	$46.30
Purchase #2	$100.26	10.819%	$111.1071	$111.11	$111.10	$111.10
Purchase #3	$146.29	13.417%	$165.9177	$165.92	$165.90	$165.90
Purchase #4	$68.30	11.195%	$75.9462	$75.95	$75.95	$75.90
Purchase #5	$180.73	9.394%	$197.7078	$197.71	$197.70	$197.70
Purchase #6	$158.98	10.541%	$175.7381	$175.74	$175.75	$175.70
Purchase #7	$94.89	4.614%	$99.2682	$99.27	$99.25	$99.30
7 purchase totals =	$793.31		$871.9574	$871.97	$871.90	$871.90