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	$54.79	12.500%	$61.6388	$61.64	$61.65	$61.60
Purchase #2	$116.79	12.498%	$131.3864	$131.39	$131.40	$131.40
Purchase #3	$40.64	5.516%	$42.8817	$42.88	$42.90	$42.90
Purchase #4	$87.57	6.375%	$93.1526	$93.15	$93.15	$93.20
Purchase #5	$23.78	8.246%	$25.7409	$25.74	$25.75	$25.70
Purchase #6	$46.78	8.168%	$50.601	$50.60	$50.60	$50.60
Purchase #7	$70.32	10.387%	$77.6241	$77.62	$77.60	$77.60
7 purchase totals =	$440.67		$483.0255	$483.02	$483.05	$483.00