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	$148.55	12.536%	$167.1722	$167.17	$167.15	$167.20
Purchase #2	$73.67	12.482%	$82.8655	$82.87	$82.85	$82.90
Purchase #3	$55.89	8.328%	$60.5445	$60.54	$60.55	$60.50
Purchase #4	$233.88	11.467%	$260.699	$260.70	$260.70	$260.70
Purchase #5	$230.58	10.111%	$253.8939	$253.89	$253.90	$253.90
Purchase #6	$155.29	9.788%	$170.4898	$170.49	$170.50	$170.50
Purchase #7	$16.58	11.524%	$18.4907	$18.49	$18.50	$18.50
7 purchase totals =	$914.44		$1,014.1556	$1,014.15	$1,014.15	$1,014.20