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	$175.58	5.211%	$184.7295	$184.73	$184.75	$184.70
Purchase #2	$67.70	3.423%	$70.0174	$70.02	$70.00	$70.00
Purchase #3	$94.38	12.447%	$106.1275	$106.13	$106.15	$106.10
Purchase #4	$15.39	11.196%	$17.1131	$17.11	$17.10	$17.10
Purchase #5	$33.69	5.256%	$35.4607	$35.46	$35.45	$35.50
Purchase #6	$47.60	10.872%	$52.7751	$52.78	$52.80	$52.80
Purchase #7	$89.47	12.800%	$100.9222	$100.92	$100.90	$100.90
7 purchase totals =	$523.81		$567.1455	$567.15	$567.15	$567.10