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	$11.95	9.165%	$13.0452	$13.05	$13.05	$13.00
Purchase #2	$212.39	10.398%	$234.4743	$234.47	$234.45	$234.50
Purchase #3	$54.32	7.608%	$58.4527	$58.45	$58.45	$58.50
Purchase #4	$146.28	13.528%	$166.0688	$166.07	$166.05	$166.10
Purchase #5	$106.54	4.701%	$111.5484	$111.55	$111.55	$111.50
Purchase #6	$58.58	3.244%	$60.4803	$60.48	$60.50	$60.50
Purchase #7	$83.59	12.706%	$94.2109	$94.21	$94.20	$94.20
7 purchase totals =	$673.65		$738.2806	$738.28	$738.25	$738.30