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	$55.58	13.161%	$62.8949	$62.89	$62.90	$62.90
Purchase #2	$21.49	3.243%	$22.1869	$22.19	$22.20	$22.20
Purchase #3	$159.62	12.683%	$179.8646	$179.86	$179.85	$179.90
Purchase #4	$50.95	4.754%	$53.3722	$53.37	$53.35	$53.40
Purchase #5	$150.33	12.765%	$169.5196	$169.52	$169.50	$169.50
Purchase #6	$34.43	12.690%	$38.7992	$38.80	$38.80	$38.80
Purchase #7	$140.54	10.728%	$155.6171	$155.62	$155.60	$155.60
7 purchase totals =	$612.94		$682.2545	$682.25	$682.20	$682.30