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	$112.41	4.761%	$117.7618	$117.76	$117.75	$117.80
Purchase #2	$199.97	7.191%	$214.3498	$214.35	$214.35	$214.30
Purchase #3	$51.99	5.465%	$54.8313	$54.83	$54.85	$54.80
Purchase #4	$62.74	7.224%	$67.2723	$67.27	$67.25	$67.30
Purchase #5	$243.68	5.417%	$256.8801	$256.88	$256.90	$256.90
Purchase #6	$22.68	12.449%	$25.5034	$25.50	$25.50	$25.50
Purchase #7	$212.70	4.806%	$222.9224	$222.92	$222.90	$222.90
7 purchase totals =	$906.17		$959.5211	$959.51	$959.50	$959.50