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	$10.74	4.309%	$11.2028	$11.20	$11.20	$11.20
Purchase #2	$78.71	7.179%	$84.3606	$84.36	$84.35	$84.40
Purchase #3	$165.75	6.136%	$175.9204	$175.92	$175.90	$175.90
Purchase #4	$152.35	13.311%	$172.6293	$172.63	$172.65	$172.60
Purchase #5	$162.43	8.218%	$175.7785	$175.78	$175.80	$175.80
Purchase #6	$179.39	13.287%	$203.2255	$203.23	$203.25	$203.20
Purchase #7	$209.53	13.733%	$238.3048	$238.30	$238.30	$238.30
7 purchase totals =	$958.90		$1,061.4219	$1,061.42	$1,061.45	$1,061.40