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	$172.30	6.141%	$182.8809	$182.88	$182.90	$182.90
Purchase #2	$34.69	8.564%	$37.6609	$37.66	$37.65	$37.70
Purchase #3	$104.85	6.521%	$111.6873	$111.69	$111.70	$111.70
Purchase #4	$54.30	4.319%	$56.6452	$56.65	$56.65	$56.60
Purchase #5	$155.58	6.331%	$165.4298	$165.43	$165.45	$165.40
Purchase #6	$20.44	3.665%	$21.1891	$21.19	$21.20	$21.20
Purchase #7	$181.60	12.168%	$203.6971	$203.70	$203.70	$203.70
7 purchase totals =	$723.76		$779.1903	$779.20	$779.25	$779.20