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	$67.41	8.770%	$73.3219	$73.32	$73.30	$73.30
Purchase #2	$93.57	7.244%	$100.3482	$100.35	$100.35	$100.30
Purchase #3	$85.50	7.447%	$91.8672	$91.87	$91.85	$91.90
Purchase #4	$39.30	7.649%	$42.3061	$42.31	$42.30	$42.30
Purchase #5	$133.77	13.680%	$152.0697	$152.07	$152.05	$152.10
Purchase #6	$9.72	9.541%	$10.6474	$10.65	$10.65	$10.60
Purchase #7	$137.90	8.481%	$149.5953	$149.60	$149.60	$149.60
7 purchase totals =	$567.17		$620.1558	$620.17	$620.10	$620.10