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	$225.35	13.656%	$256.1238	$256.12	$256.10	$256.10
Purchase #2	$143.38	5.540%	$151.3233	$151.32	$151.30	$151.30
Purchase #3	$57.98	5.549%	$61.1973	$61.20	$61.20	$61.20
Purchase #4	$197.79	8.139%	$213.8881	$213.89	$213.90	$213.90
Purchase #5	$183.57	9.167%	$200.3979	$200.40	$200.40	$200.40
Purchase #6	$75.41	8.272%	$81.6479	$81.65	$81.65	$81.60
Purchase #7	$32.98	11.792%	$36.869	$36.87	$36.85	$36.90
7 purchase totals =	$916.46		$1,001.4473	$1,001.45	$1,001.40	$1,001.40