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	$208.57	12.767%	$235.1981	$235.20	$235.20	$235.20
Purchase #2	$11.51	12.145%	$12.9079	$12.91	$12.90	$12.90
Purchase #3	$186.56	7.143%	$199.886	$199.89	$199.90	$199.90
Purchase #4	$200.57	5.672%	$211.9463	$211.95	$211.95	$211.90
Purchase #5	$98.65	11.449%	$109.9444	$109.94	$109.95	$109.90
Purchase #6	$184.77	8.544%	$200.5567	$200.56	$200.55	$200.60
Purchase #7	$107.35	7.591%	$115.4989	$115.50	$115.50	$115.50
7 purchase totals =	$997.98		$1,085.9383	$1,085.95	$1,085.95	$1,085.90