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	$199.58	5.328%	$210.2136	$210.21	$210.20	$210.20
Purchase #2	$49.54	8.447%	$53.7246	$53.72	$53.70	$53.70
Purchase #3	$90.75	11.756%	$101.4186	$101.42	$101.40	$101.40
Purchase #4	$43.68	4.283%	$45.5508	$45.55	$45.55	$45.60
Purchase #5	$30.86	5.282%	$32.49	$32.49	$32.50	$32.50
Purchase #6	$32.94	9.351%	$36.0202	$36.02	$36.00	$36.00
Purchase #7	$40.59	11.148%	$45.115	$45.12	$45.10	$45.10
7 purchase totals =	$487.94		$524.5328	$524.53	$524.45	$524.50