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	$80.31	10.735%	$88.9313	$88.93	$88.95	$88.90
Purchase #2	$37.59	8.519%	$40.7923	$40.79	$40.80	$40.80
Purchase #3	$109.99	12.401%	$123.6299	$123.63	$123.65	$123.60
Purchase #4	$129.83	12.689%	$146.3041	$146.30	$146.30	$146.30
Purchase #5	$41.70	6.407%	$44.3717	$44.37	$44.35	$44.40
Purchase #6	$224.49	13.668%	$255.1733	$255.17	$255.15	$255.20
Purchase #7	$48.72	13.190%	$55.1462	$55.15	$55.15	$55.10
7 purchase totals =	$672.63		$754.3488	$754.34	$754.35	$754.30