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	$153.36	12.720%	$172.8674	$172.87	$172.85	$172.90
Purchase #2	$190.34	8.478%	$206.477	$206.48	$206.50	$206.50
Purchase #3	$211.58	8.605%	$229.7865	$229.79	$229.80	$229.80
Purchase #4	$131.82	11.313%	$146.7328	$146.73	$146.75	$146.70
Purchase #5	$109.83	6.204%	$116.6439	$116.64	$116.65	$116.60
Purchase #6	$137.39	9.802%	$150.857	$150.86	$150.85	$150.90
Purchase #7	$228.46	11.641%	$255.055	$255.06	$255.05	$255.10
7 purchase totals =	$1,162.78		$1,278.4196	$1,278.43	$1,278.45	$1,278.50