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	$204.38	8.161%	$221.0595	$221.06	$221.05	$221.10
Purchase #2	$34.72	3.485%	$35.93	$35.93	$35.95	$35.90
Purchase #3	$152.26	9.367%	$166.5222	$166.52	$166.50	$166.50
Purchase #4	$80.83	13.584%	$91.8099	$91.81	$91.80	$91.80
Purchase #5	$206.82	4.555%	$216.2407	$216.24	$216.25	$216.20
Purchase #6	$172.37	13.839%	$196.2243	$196.22	$196.20	$196.20
Purchase #7	$25.77	3.250%	$26.6075	$26.61	$26.60	$26.60
7 purchase totals =	$877.15		$954.3941	$954.39	$954.35	$954.30