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	$30.90	6.247%	$32.8303	$32.83	$32.85	$32.80
Purchase #2	$11.39	8.243%	$12.3289	$12.33	$12.35	$12.30
Purchase #3	$55.92	9.447%	$61.2028	$61.20	$61.20	$61.20
Purchase #4	$45.78	11.720%	$51.1454	$51.15	$51.15	$51.10
Purchase #5	$200.53	11.851%	$224.2948	$224.29	$224.30	$224.30
Purchase #6	$146.99	13.173%	$166.353	$166.35	$166.35	$166.40
Purchase #7	$151.61	8.345%	$164.2619	$164.26	$164.25	$164.30
7 purchase totals =	$643.12		$712.4171	$712.41	$712.45	$712.40