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	$135.53	11.204%	$150.7148	$150.71	$150.70	$150.70
Purchase #2	$40.58	13.721%	$46.148	$46.15	$46.15	$46.10
Purchase #3	$26.60	5.172%	$27.9758	$27.98	$28.00	$28.00
Purchase #4	$54.45	8.648%	$59.1588	$59.16	$59.15	$59.20
Purchase #5	$228.77	11.324%	$254.6759	$254.68	$254.70	$254.70
Purchase #6	$34.90	7.487%	$37.513	$37.51	$37.50	$37.50
Purchase #7	$173.67	9.601%	$190.3441	$190.34	$190.35	$190.30
7 purchase totals =	$694.50		$766.5304	$766.53	$766.55	$766.50