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	$205.93	3.637%	$213.4197	$213.42	$213.40	$213.40
Purchase #2	$187.43	13.788%	$213.2728	$213.27	$213.25	$213.30
Purchase #3	$10.27	3.370%	$10.6161	$10.62	$10.60	$10.60
Purchase #4	$22.98	9.580%	$25.1815	$25.18	$25.20	$25.20
Purchase #5	$179.53	11.432%	$200.0539	$200.05	$200.05	$200.10
Purchase #6	$59.91	4.198%	$62.425	$62.43	$62.45	$62.40
Purchase #7	$34.25	9.592%	$37.5353	$37.54	$37.55	$37.50
7 purchase totals =	$700.30		$762.5043	$762.51	$762.50	$762.50