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	$95.30	10.315%	$105.1302	$105.13	$105.15	$105.10
Purchase #2	$161.49	9.429%	$176.7169	$176.72	$176.70	$176.70
Purchase #3	$203.92	9.695%	$223.69	$223.69	$223.70	$223.70
Purchase #4	$203.64	3.105%	$209.963	$209.96	$209.95	$210.00
Purchase #5	$79.73	4.567%	$83.3713	$83.37	$83.35	$83.40
Purchase #6	$67.88	13.512%	$77.0519	$77.05	$77.05	$77.10
Purchase #7	$117.68	8.106%	$127.2191	$127.22	$127.20	$127.20
7 purchase totals =	$929.64		$1,003.1424	$1,003.14	$1,003.10	$1,003.20