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	$250.89	7.636%	$270.048	$270.05	$270.05	$270.00
Purchase #2	$11.92	6.476%	$12.6919	$12.69	$12.70	$12.70
Purchase #3	$125.30	12.274%	$140.6793	$140.68	$140.70	$140.70
Purchase #4	$20.90	8.696%	$22.7175	$22.72	$22.70	$22.70
Purchase #5	$125.35	11.377%	$139.6111	$139.61	$139.60	$139.60
Purchase #6	$144.67	5.483%	$152.6023	$152.60	$152.60	$152.60
Purchase #7	$31.56	7.171%	$33.8232	$33.82	$33.80	$33.80
7 purchase totals =	$710.59		$772.1733	$772.17	$772.15	$772.10