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	$48.89	9.309%	$53.4412	$53.44	$53.45	$53.40
Purchase #2	$70.51	9.770%	$77.3988	$77.40	$77.40	$77.40
Purchase #3	$91.47	13.471%	$103.7919	$103.79	$103.80	$103.80
Purchase #4	$47.34	8.453%	$51.3417	$51.34	$51.35	$51.30
Purchase #5	$146.56	5.484%	$154.5974	$154.60	$154.60	$154.60
Purchase #6	$211.37	7.153%	$226.4893	$226.49	$226.50	$226.50
Purchase #7	$182.68	7.327%	$196.065	$196.07	$196.05	$196.10
7 purchase totals =	$798.82		$863.1253	$863.13	$863.15	$863.10