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	$104.28	13.820%	$118.6915	$118.69	$118.70	$118.70
Purchase #2	$247.51	10.390%	$273.2263	$273.23	$273.25	$273.20
Purchase #3	$172.35	10.451%	$190.3623	$190.36	$190.35	$190.40
Purchase #4	$119.79	8.854%	$130.3962	$130.40	$130.40	$130.40
Purchase #5	$97.26	7.216%	$104.2783	$104.28	$104.30	$104.30
Purchase #6	$145.40	4.426%	$151.8354	$151.84	$151.85	$151.80
Purchase #7	$62.43	3.287%	$64.4821	$64.48	$64.50	$64.50
7 purchase totals =	$949.02		$1,033.2721	$1,033.28	$1,033.35	$1,033.30