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	$86.81	4.195%	$90.4517	$90.45	$90.45	$90.50
Purchase #2	$15.57	7.792%	$16.7832	$16.78	$16.80	$16.80
Purchase #3	$124.62	5.222%	$131.1277	$131.13	$131.15	$131.10
Purchase #4	$71.45	4.824%	$74.8967	$74.90	$74.90	$74.90
Purchase #5	$17.93	11.749%	$20.0366	$20.04	$20.05	$20.00
Purchase #6	$61.82	6.421%	$65.7895	$65.79	$65.80	$65.80
Purchase #7	$156.65	7.871%	$168.9799	$168.98	$169.00	$169.00
7 purchase totals =	$534.85		$568.0653	$568.07	$568.15	$568.10