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	$46.96	13.181%	$53.1498	$53.15	$53.15	$53.10
Purchase #2	$127.95	10.821%	$141.7955	$141.80	$141.80	$141.80
Purchase #3	$180.28	10.669%	$199.5141	$199.51	$199.50	$199.50
Purchase #4	$200.36	10.562%	$221.522	$221.52	$221.50	$221.50
Purchase #5	$32.28	4.638%	$33.7771	$33.78	$33.80	$33.80
Purchase #6	$165.36	5.513%	$174.4763	$174.48	$174.50	$174.50
Purchase #7	$93.66	10.339%	$103.3435	$103.34	$103.35	$103.30
7 purchase totals =	$846.85		$927.5783	$927.58	$927.60	$927.50