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	$216.81	8.198%	$234.5841	$234.58	$234.60	$234.60
Purchase #2	$198.57	13.328%	$225.0354	$225.04	$225.05	$225.00
Purchase #3	$168.80	13.545%	$191.664	$191.66	$191.65	$191.70
Purchase #4	$35.68	5.179%	$37.5279	$37.53	$37.55	$37.50
Purchase #5	$73.82	10.729%	$81.7401	$81.74	$81.75	$81.70
Purchase #6	$62.38	7.625%	$67.1365	$67.14	$67.15	$67.10
Purchase #7	$54.57	8.330%	$59.1157	$59.12	$59.10	$59.10
7 purchase totals =	$810.63		$896.8037	$896.81	$896.85	$896.70