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	$152.51	13.551%	$173.1766	$173.18	$173.20	$173.20
Purchase #2	$94.35	5.430%	$99.4732	$99.47	$99.45	$99.50
Purchase #3	$82.89	13.305%	$93.9185	$93.92	$93.90	$93.90
Purchase #4	$92.42	9.828%	$101.503	$101.50	$101.50	$101.50
Purchase #5	$209.46	9.361%	$229.0676	$229.07	$229.05	$229.10
Purchase #6	$159.48	4.592%	$166.8033	$166.80	$166.80	$166.80
Purchase #7	$81.84	10.670%	$90.5723	$90.57	$90.55	$90.60
7 purchase totals =	$872.95		$954.5145	$954.51	$954.45	$954.60