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	$185.66	5.872%	$196.562	$196.56	$196.55	$196.60
Purchase #2	$32.42	7.406%	$34.821	$34.82	$34.80	$34.80
Purchase #3	$204.81	8.536%	$222.2926	$222.29	$222.30	$222.30
Purchase #4	$158.60	10.851%	$175.8097	$175.81	$175.80	$175.80
Purchase #5	$28.62	10.195%	$31.5378	$31.54	$31.55	$31.50
Purchase #6	$17.89	12.687%	$20.1597	$20.16	$20.15	$20.20
Purchase #7	$113.43	7.799%	$122.2764	$122.28	$122.30	$122.30
7 purchase totals =	$741.43		$803.4592	$803.46	$803.45	$803.50