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	$153.49	12.540%	$172.7376	$172.74	$172.75	$172.70
Purchase #2	$90.85	9.105%	$99.1219	$99.12	$99.10	$99.10
Purchase #3	$34.45	9.191%	$37.6163	$37.62	$37.60	$37.60
Purchase #4	$178.51	12.125%	$200.1543	$200.15	$200.15	$200.20
Purchase #5	$6.30	4.494%	$6.5831	$6.58	$6.60	$6.60
Purchase #6	$203.50	13.641%	$231.2594	$231.26	$231.25	$231.30
Purchase #7	$114.92	3.803%	$119.2904	$119.29	$119.30	$119.30
7 purchase totals =	$782.02		$866.7630	$866.76	$866.75	$866.80