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	$135.84	11.560%	$151.5431	$151.54	$151.55	$151.50
Purchase #2	$247.58	11.460%	$275.9527	$275.95	$275.95	$276.00
Purchase #3	$119.37	3.763%	$123.8619	$123.86	$123.85	$123.90
Purchase #4	$31.79	8.555%	$34.5096	$34.51	$34.50	$34.50
Purchase #5	$80.82	7.388%	$86.791	$86.79	$86.80	$86.80
Purchase #6	$248.52	6.330%	$264.2513	$264.25	$264.25	$264.30
Purchase #7	$155.50	13.792%	$176.9466	$176.95	$176.95	$176.90
7 purchase totals =	$1,019.42		$1,113.8562	$1,113.85	$1,113.85	$1,113.90