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	$208.59	6.622%	$222.4028	$222.40	$222.40	$222.40
Purchase #2	$123.59	11.302%	$137.5581	$137.56	$137.55	$137.60
Purchase #3	$167.75	7.738%	$180.7305	$180.73	$180.75	$180.70
Purchase #4	$146.39	8.367%	$158.6385	$158.64	$158.65	$158.60
Purchase #5	$117.57	11.215%	$130.7555	$130.76	$130.75	$130.80
Purchase #6	$179.70	5.682%	$189.9106	$189.91	$189.90	$189.90
Purchase #7	$221.56	10.309%	$244.4006	$244.40	$244.40	$244.40
7 purchase totals =	$1,165.15		$1,264.3966	$1,264.40	$1,264.40	$1,264.40