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	$50.86	8.549%	$55.208	$55.21	$55.20	$55.20
Purchase #2	$110.66	11.671%	$123.5751	$123.58	$123.60	$123.60
Purchase #3	$81.63	10.844%	$90.482	$90.48	$90.50	$90.50
Purchase #4	$203.53	8.873%	$221.5892	$221.59	$221.60	$221.60
Purchase #5	$113.49	11.297%	$126.311	$126.31	$126.30	$126.30
Purchase #6	$120.39	8.631%	$130.7809	$130.78	$130.80	$130.80
Purchase #7	$13.59	4.831%	$14.2465	$14.25	$14.25	$14.20
7 purchase totals =	$694.15		$762.1927	$762.20	$762.25	$762.20