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	$97.38	11.240%	$108.3255	$108.33	$108.35	$108.30
Purchase #2	$50.55	9.535%	$55.3699	$55.37	$55.35	$55.40
Purchase #3	$108.68	7.564%	$116.9006	$116.90	$116.90	$116.90
Purchase #4	$172.49	6.350%	$183.4431	$183.44	$183.45	$183.40
Purchase #5	$130.40	7.672%	$140.4043	$140.40	$140.40	$140.40
Purchase #6	$63.82	3.202%	$65.8635	$65.86	$65.85	$65.90
Purchase #7	$71.87	8.826%	$78.2132	$78.21	$78.20	$78.20
7 purchase totals =	$695.19		$748.5201	$748.51	$748.50	$748.50