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	$205.59	7.603%	$221.221	$221.22	$221.20	$221.20
Purchase #2	$95.26	9.579%	$104.385	$104.39	$104.40	$104.40
Purchase #3	$226.31	4.500%	$236.494	$236.49	$236.50	$236.50
Purchase #4	$151.41	5.371%	$159.5422	$159.54	$159.55	$159.50
Purchase #5	$9.40	11.521%	$10.483	$10.48	$10.50	$10.50
Purchase #6	$37.74	12.642%	$42.5111	$42.51	$42.50	$42.50
Purchase #7	$63.86	11.328%	$71.0941	$71.09	$71.10	$71.10
7 purchase totals =	$789.57		$845.7304	$845.72	$845.75	$845.70