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	$96.34	5.505%	$101.6435	$101.64	$101.65	$101.60
Purchase #2	$71.98	13.701%	$81.842	$81.84	$81.85	$81.80
Purchase #3	$138.67	5.136%	$145.7921	$145.79	$145.80	$145.80
Purchase #4	$11.58	5.594%	$12.2278	$12.23	$12.25	$12.20
Purchase #5	$37.50	5.573%	$39.5899	$39.59	$39.60	$39.60
Purchase #6	$5.29	11.682%	$5.908	$5.91	$5.90	$5.90
Purchase #7	$120.69	9.277%	$131.8864	$131.89	$131.90	$131.90
7 purchase totals =	$482.05		$518.8897	$518.89	$518.95	$518.80