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	$61.38	8.580%	$66.6464	$66.65	$66.65	$66.60
Purchase #2	$44.62	12.589%	$50.2372	$50.24	$50.25	$50.20
Purchase #3	$45.37	3.105%	$46.7787	$46.78	$46.80	$46.80
Purchase #4	$145.93	13.665%	$165.8713	$165.87	$165.85	$165.90
Purchase #5	$183.73	7.796%	$198.0536	$198.05	$198.05	$198.10
Purchase #6	$59.71	12.696%	$67.2908	$67.29	$67.30	$67.30
Purchase #7	$26.63	6.105%	$28.2558	$28.26	$28.25	$28.30
7 purchase totals =	$567.37		$623.1338	$623.14	$623.15	$623.20