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	$130.50	7.376%	$140.1257	$140.13	$140.15	$140.10
Purchase #2	$76.91	6.662%	$82.0337	$82.03	$82.05	$82.00
Purchase #3	$230.56	11.417%	$256.883	$256.88	$256.90	$256.90
Purchase #4	$69.44	4.722%	$72.719	$72.72	$72.70	$72.70
Purchase #5	$146.75	5.359%	$154.6143	$154.61	$154.60	$154.60
Purchase #6	$136.56	13.820%	$155.4326	$155.43	$155.45	$155.40
Purchase #7	$245.57	10.765%	$272.0056	$272.01	$272.00	$272.00
7 purchase totals =	$1,036.29		$1,133.8139	$1,133.81	$1,133.85	$1,133.70