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	$42.76	5.479%	$45.1028	$45.10	$45.10	$45.10
Purchase #2	$95.54	10.421%	$105.4962	$105.50	$105.50	$105.50
Purchase #3	$101.43	10.108%	$111.6825	$111.68	$111.70	$111.70
Purchase #4	$8.79	7.528%	$9.4517	$9.45	$9.45	$9.50
Purchase #5	$159.33	10.528%	$176.1043	$176.10	$176.10	$176.10
Purchase #6	$72.65	7.651%	$78.2085	$78.21	$78.20	$78.20
Purchase #7	$234.60	10.434%	$259.0782	$259.08	$259.10	$259.10
7 purchase totals =	$715.10		$785.1242	$785.12	$785.15	$785.20