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	$154.47	10.776%	$171.1157	$171.12	$171.10	$171.10
Purchase #2	$35.60	4.594%	$37.2355	$37.24	$37.25	$37.20
Purchase #3	$111.65	6.447%	$118.8481	$118.85	$118.85	$118.80
Purchase #4	$48.84	4.128%	$50.8561	$50.86	$50.85	$50.90
Purchase #5	$235.27	5.584%	$248.4075	$248.41	$248.40	$248.40
Purchase #6	$40.38	11.855%	$45.167	$45.17	$45.15	$45.20
Purchase #7	$42.74	12.208%	$47.9577	$47.96	$47.95	$48.00
7 purchase totals =	$668.95		$719.5876	$719.61	$719.55	$719.60