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	$232.77	13.624%	$264.4826	$264.48	$264.50	$264.50
Purchase #2	$70.81	5.736%	$74.8717	$74.87	$74.85	$74.90
Purchase #3	$15.75	7.339%	$16.9059	$16.91	$16.90	$16.90
Purchase #4	$30.27	8.592%	$32.8708	$32.87	$32.85	$32.90
Purchase #5	$208.60	7.341%	$223.9133	$223.91	$223.90	$223.90
Purchase #6	$233.48	8.429%	$253.16	$253.16	$253.15	$253.20
Purchase #7	$223.79	9.546%	$245.153	$245.15	$245.15	$245.20
7 purchase totals =	$1,015.47		$1,111.3573	$1,111.35	$1,111.30	$1,111.50