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	$155.94	8.630%	$169.3976	$169.40	$169.40	$169.40
Purchase #2	$229.73	13.234%	$260.1325	$260.13	$260.15	$260.10
Purchase #3	$68.67	11.394%	$76.4943	$76.49	$76.50	$76.50
Purchase #4	$158.52	8.616%	$172.1781	$172.18	$172.20	$172.20
Purchase #5	$160.82	3.133%	$165.8585	$165.86	$165.85	$165.90
Purchase #6	$136.78	4.218%	$142.5494	$142.55	$142.55	$142.50
Purchase #7	$180.25	4.795%	$188.893	$188.89	$188.90	$188.90
7 purchase totals =	$1,090.71		$1,175.5034	$1,175.50	$1,175.55	$1,175.50