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	$42.67	7.239%	$45.7589	$45.76	$45.75	$45.80
Purchase #2	$67.25	4.773%	$70.4598	$70.46	$70.45	$70.50
Purchase #3	$167.81	9.331%	$183.4684	$183.47	$183.45	$183.50
Purchase #4	$151.28	11.684%	$168.9556	$168.96	$168.95	$169.00
Purchase #5	$82.83	13.738%	$94.2092	$94.21	$94.20	$94.20
Purchase #6	$179.86	13.693%	$204.4882	$204.49	$204.50	$204.50
Purchase #7	$121.79	9.632%	$133.5208	$133.52	$133.50	$133.50
7 purchase totals =	$813.49		$900.8609	$900.87	$900.80	$901.00