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	$190.54	11.394%	$212.2501	$212.25	$212.25	$212.30
Purchase #2	$146.80	13.851%	$167.1333	$167.13	$167.15	$167.10
Purchase #3	$200.41	10.594%	$221.6414	$221.64	$221.65	$221.60
Purchase #4	$20.27	9.762%	$22.2488	$22.25	$22.25	$22.20
Purchase #5	$220.37	5.233%	$231.902	$231.90	$231.90	$231.90
Purchase #6	$33.41	12.595%	$37.618	$37.62	$37.60	$37.60
Purchase #7	$137.47	10.342%	$151.6871	$151.69	$151.70	$151.70
7 purchase totals =	$949.27		$1,044.4807	$1,044.48	$1,044.50	$1,044.40