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	$152.79	10.371%	$168.6359	$168.64	$168.65	$168.60
Purchase #2	$235.31	7.613%	$253.2242	$253.22	$253.20	$253.20
Purchase #3	$120.78	9.166%	$131.8507	$131.85	$131.85	$131.90
Purchase #4	$131.66	9.856%	$144.6364	$144.64	$144.65	$144.60
Purchase #5	$197.69	13.600%	$224.5758	$224.58	$224.60	$224.60
Purchase #6	$71.57	11.230%	$79.6073	$79.61	$79.60	$79.60
Purchase #7	$147.75	11.784%	$165.1609	$165.16	$165.15	$165.20
7 purchase totals =	$1,057.55		$1,167.6912	$1,167.70	$1,167.70	$1,167.70