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	$162.92	4.616%	$170.4404	$170.44	$170.45	$170.40
Purchase #2	$124.86	11.798%	$139.591	$139.59	$139.60	$139.60
Purchase #3	$200.78	13.363%	$227.6102	$227.61	$227.60	$227.60
Purchase #4	$99.55	13.693%	$113.1814	$113.18	$113.20	$113.20
Purchase #5	$28.90	13.515%	$32.8058	$32.81	$32.80	$32.80
Purchase #6	$30.43	8.214%	$32.9295	$32.93	$32.95	$32.90
Purchase #7	$165.71	8.702%	$180.1301	$180.13	$180.15	$180.10
7 purchase totals =	$813.15		$896.6884	$896.69	$896.75	$896.60