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	$100.26	11.596%	$111.8861	$111.89	$111.90	$111.90
Purchase #2	$16.50	13.747%	$18.7683	$18.77	$18.75	$18.80
Purchase #3	$79.39	5.459%	$83.7239	$83.72	$83.70	$83.70
Purchase #4	$49.39	10.226%	$54.4406	$54.44	$54.45	$54.40
Purchase #5	$45.46	6.719%	$48.5145	$48.51	$48.50	$48.50
Purchase #6	$200.28	8.733%	$217.7705	$217.77	$217.75	$217.80
Purchase #7	$144.43	10.453%	$159.5273	$159.53	$159.55	$159.50
7 purchase totals =	$635.71		$694.6312	$694.63	$694.60	$694.60