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	$217.86	3.449%	$225.374	$225.37	$225.35	$225.40
Purchase #2	$183.30	7.384%	$196.8349	$196.83	$196.85	$196.80
Purchase #3	$116.61	7.377%	$125.2123	$125.21	$125.20	$125.20
Purchase #4	$91.92	9.557%	$100.7048	$100.70	$100.70	$100.70
Purchase #5	$120.66	4.325%	$125.8785	$125.88	$125.90	$125.90
Purchase #6	$111.25	4.804%	$116.5945	$116.59	$116.60	$116.60
Purchase #7	$67.90	11.697%	$75.8423	$75.84	$75.85	$75.80
7 purchase totals =	$909.50		$966.4413	$966.42	$966.45	$966.40