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	$81.73	12.762%	$92.1604	$92.16	$92.15	$92.20
Purchase #2	$29.54	12.240%	$33.1557	$33.16	$33.15	$33.20
Purchase #3	$116.56	11.589%	$130.0681	$130.07	$130.05	$130.10
Purchase #4	$160.41	8.337%	$173.7834	$173.78	$173.80	$173.80
Purchase #5	$81.72	4.649%	$85.5192	$85.52	$85.50	$85.50
Purchase #6	$173.55	7.757%	$187.0123	$187.01	$187.00	$187.00
Purchase #7	$92.70	13.645%	$105.3489	$105.35	$105.35	$105.30
7 purchase totals =	$736.21		$807.0480	$807.05	$807.00	$807.10