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	$175.98	7.257%	$188.7509	$188.75	$188.75	$188.80
Purchase #2	$208.55	6.261%	$221.6073	$221.61	$221.60	$221.60
Purchase #3	$214.89	13.343%	$243.5628	$243.56	$243.55	$243.60
Purchase #4	$181.33	8.613%	$196.948	$196.95	$196.95	$196.90
Purchase #5	$139.31	3.102%	$143.6314	$143.63	$143.65	$143.60
Purchase #6	$102.28	5.723%	$108.1335	$108.13	$108.15	$108.10
Purchase #7	$214.96	7.593%	$231.2819	$231.28	$231.30	$231.30
7 purchase totals =	$1,237.30		$1,333.9158	$1,333.91	$1,333.95	$1,333.90