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	$186.61	11.601%	$208.2586	$208.26	$208.25	$208.30
Purchase #2	$148.29	7.755%	$159.7899	$159.79	$159.80	$159.80
Purchase #3	$170.84	4.738%	$178.9344	$178.93	$178.95	$178.90
Purchase #4	$217.69	13.760%	$247.6441	$247.64	$247.65	$247.60
Purchase #5	$31.42	7.417%	$33.7504	$33.75	$33.75	$33.80
Purchase #6	$74.96	4.735%	$78.5094	$78.51	$78.50	$78.50
Purchase #7	$55.31	10.820%	$61.2945	$61.29	$61.30	$61.30
7 purchase totals =	$885.12		$968.1813	$968.17	$968.20	$968.20