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	$145.81	12.657%	$164.2652	$164.27	$164.25	$164.30
Purchase #2	$26.53	5.185%	$27.9056	$27.91	$27.90	$27.90
Purchase #3	$226.25	4.241%	$235.8453	$235.85	$235.85	$235.80
Purchase #4	$133.77	13.457%	$151.7714	$151.77	$151.75	$151.80
Purchase #5	$115.75	7.443%	$124.3653	$124.37	$124.35	$124.40
Purchase #6	$154.89	11.383%	$172.5211	$172.52	$172.50	$172.50
Purchase #7	$140.52	13.263%	$159.1572	$159.16	$159.15	$159.20
7 purchase totals =	$943.52		$1,035.8311	$1,035.85	$1,035.75	$1,035.90