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	$113.67	12.428%	$127.7969	$127.80	$127.80	$127.80
Purchase #2	$19.38	5.636%	$20.4723	$20.47	$20.45	$20.50
Purchase #3	$54.62	4.589%	$57.1265	$57.13	$57.15	$57.10
Purchase #4	$118.34	10.252%	$130.4722	$130.47	$130.45	$130.50
Purchase #5	$201.71	11.621%	$225.1507	$225.15	$225.15	$225.20
Purchase #6	$192.39	6.608%	$205.1031	$205.10	$205.10	$205.10
Purchase #7	$93.77	12.107%	$105.1227	$105.12	$105.10	$105.10
7 purchase totals =	$793.88		$871.2444	$871.24	$871.20	$871.30