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	$41.76	12.377%	$46.9286	$46.93	$46.95	$46.90
Purchase #2	$94.54	11.260%	$105.1852	$105.19	$105.20	$105.20
Purchase #3	$144.35	3.402%	$149.2608	$149.26	$149.25	$149.30
Purchase #4	$130.95	4.198%	$136.4473	$136.45	$136.45	$136.40
Purchase #5	$11.69	10.631%	$12.9328	$12.93	$12.95	$12.90
Purchase #6	$53.82	13.469%	$61.069	$61.07	$61.05	$61.10
Purchase #7	$74.47	10.153%	$82.0309	$82.03	$82.05	$82.00
7 purchase totals =	$551.58		$593.8546	$593.86	$593.90	$593.80