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	$80.94	5.151%	$85.1092	$85.11	$85.10	$85.10
Purchase #2	$55.57	11.228%	$61.8094	$61.81	$61.80	$61.80
Purchase #3	$92.56	8.626%	$100.5442	$100.54	$100.55	$100.50
Purchase #4	$68.69	10.733%	$76.0625	$76.06	$76.05	$76.10
Purchase #5	$145.85	6.734%	$155.6715	$155.67	$155.65	$155.70
Purchase #6	$175.29	10.571%	$193.8199	$193.82	$193.80	$193.80
Purchase #7	$236.60	8.521%	$256.7607	$256.76	$256.75	$256.80
7 purchase totals =	$855.50		$929.7774	$929.77	$929.70	$929.80