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	$219.65	4.625%	$229.8088	$229.81	$229.80	$229.80
Purchase #2	$75.52	10.377%	$83.3567	$83.36	$83.35	$83.40
Purchase #3	$149.75	13.307%	$169.6772	$169.68	$169.70	$169.70
Purchase #4	$42.71	9.837%	$46.9114	$46.91	$46.90	$46.90
Purchase #5	$73.91	12.191%	$82.9204	$82.92	$82.90	$82.90
Purchase #6	$100.30	11.484%	$111.8185	$111.82	$111.80	$111.80
Purchase #7	$223.37	3.554%	$231.3086	$231.31	$231.30	$231.30
7 purchase totals =	$885.21		$955.8016	$955.81	$955.75	$955.80