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	$97.29	3.506%	$100.701	$100.70	$100.70	$100.70
Purchase #2	$169.90	12.749%	$191.5606	$191.56	$191.55	$191.60
Purchase #3	$181.81	8.162%	$196.6493	$196.65	$196.65	$196.60
Purchase #4	$90.31	12.727%	$101.8038	$101.80	$101.80	$101.80
Purchase #5	$59.50	12.864%	$67.1541	$67.15	$67.15	$67.20
Purchase #6	$64.62	11.104%	$71.7954	$71.80	$71.80	$71.80
Purchase #7	$116.81	13.716%	$132.8317	$132.83	$132.85	$132.80
7 purchase totals =	$780.24		$862.4959	$862.49	$862.50	$862.50