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	$198.82	11.423%	$221.5312	$221.53	$221.55	$221.50
Purchase #2	$64.81	10.677%	$71.7298	$71.73	$71.75	$71.70
Purchase #3	$222.71	13.522%	$252.8248	$252.82	$252.80	$252.80
Purchase #4	$26.54	13.253%	$30.0573	$30.06	$30.05	$30.10
Purchase #5	$36.89	9.702%	$40.4691	$40.47	$40.45	$40.50
Purchase #6	$158.39	5.619%	$167.2899	$167.29	$167.30	$167.30
Purchase #7	$166.84	3.402%	$172.5159	$172.52	$172.50	$172.50
7 purchase totals =	$875.00		$956.4180	$956.42	$956.40	$956.40