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	$136.47	13.663%	$155.1159	$155.12	$155.10	$155.10
Purchase #2	$87.40	4.249%	$91.1136	$91.11	$91.10	$91.10
Purchase #3	$139.81	8.113%	$151.1528	$151.15	$151.15	$151.20
Purchase #4	$229.52	11.380%	$255.6394	$255.64	$255.65	$255.60
Purchase #5	$34.62	5.511%	$36.5279	$36.53	$36.55	$36.50
Purchase #6	$137.65	6.681%	$146.8464	$146.85	$146.85	$146.80
Purchase #7	$176.33	13.754%	$200.5824	$200.58	$200.60	$200.60
7 purchase totals =	$941.80		$1,036.9784	$1,036.98	$1,037.00	$1,036.90