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	$58.88	11.640%	$65.7336	$65.73	$65.75	$65.70
Purchase #2	$133.72	8.274%	$144.784	$144.78	$144.80	$144.80
Purchase #3	$103.48	3.215%	$106.8069	$106.81	$106.80	$106.80
Purchase #4	$204.87	8.438%	$222.1569	$222.16	$222.15	$222.20
Purchase #5	$131.34	13.553%	$149.1405	$149.14	$149.15	$149.10
Purchase #6	$138.89	8.769%	$151.0693	$151.07	$151.05	$151.10
Purchase #7	$204.34	11.849%	$228.5522	$228.55	$228.55	$228.60
7 purchase totals =	$975.52		$1,068.2434	$1,068.24	$1,068.25	$1,068.30