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	$44.52	3.177%	$45.9344	$45.93	$45.95	$45.90
Purchase #2	$189.53	6.440%	$201.7357	$201.74	$201.75	$201.70
Purchase #3	$133.32	13.705%	$151.5915	$151.59	$151.60	$151.60
Purchase #4	$126.27	9.120%	$137.7858	$137.79	$137.80	$137.80
Purchase #5	$221.64	9.849%	$243.4693	$243.47	$243.45	$243.50
Purchase #6	$59.41	13.588%	$67.4826	$67.48	$67.50	$67.50
Purchase #7	$93.67	10.394%	$103.4061	$103.41	$103.40	$103.40
7 purchase totals =	$868.36		$951.4054	$951.41	$951.45	$951.40