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	$147.90	10.495%	$163.4221	$163.42	$163.40	$163.40
Purchase #2	$155.92	10.638%	$172.5068	$172.51	$172.50	$172.50
Purchase #3	$136.98	8.605%	$148.7671	$148.77	$148.75	$148.80
Purchase #4	$38.96	8.419%	$42.24	$42.24	$42.25	$42.20
Purchase #5	$75.58	8.802%	$82.2326	$82.23	$82.25	$82.20
Purchase #6	$163.29	6.197%	$173.4091	$173.41	$173.40	$173.40
Purchase #7	$94.31	12.253%	$105.8658	$105.87	$105.85	$105.90
7 purchase totals =	$812.94		$888.4435	$888.45	$888.40	$888.40