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	$42.91	10.766%	$47.5297	$47.53	$47.55	$47.50
Purchase #2	$62.77	4.465%	$65.5727	$65.57	$65.55	$65.60
Purchase #3	$37.93	8.451%	$41.1355	$41.14	$41.15	$41.10
Purchase #4	$18.42	13.686%	$20.941	$20.94	$20.95	$20.90
Purchase #5	$140.95	10.134%	$155.2339	$155.23	$155.25	$155.20
Purchase #6	$13.72	11.413%	$15.2859	$15.29	$15.30	$15.30
Purchase #7	$149.82	12.438%	$168.4546	$168.45	$168.45	$168.50
7 purchase totals =	$466.52		$514.1533	$514.15	$514.20	$514.10