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	$89.69	7.481%	$96.3997	$96.40	$96.40	$96.40
Purchase #2	$124.85	5.723%	$131.9952	$132.00	$132.00	$132.00
Purchase #3	$192.54	7.327%	$206.6474	$206.65	$206.65	$206.60
Purchase #4	$43.26	5.148%	$45.487	$45.49	$45.50	$45.50
Purchase #5	$145.33	13.756%	$165.3216	$165.32	$165.30	$165.30
Purchase #6	$78.37	12.377%	$88.0699	$88.07	$88.05	$88.10
Purchase #7	$131.39	4.707%	$137.5745	$137.57	$137.55	$137.60
7 purchase totals =	$805.43		$871.4953	$871.50	$871.45	$871.50