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	$171.53	8.185%	$185.5697	$185.57	$185.55	$185.60
Purchase #2	$77.61	10.105%	$85.4525	$85.45	$85.45	$85.50
Purchase #3	$203.89	3.280%	$210.5776	$210.58	$210.60	$210.60
Purchase #4	$195.95	13.219%	$221.8526	$221.85	$221.85	$221.90
Purchase #5	$155.55	11.753%	$173.8318	$173.83	$173.85	$173.80
Purchase #6	$236.44	8.525%	$256.5965	$256.60	$256.60	$256.60
Purchase #7	$212.77	11.855%	$237.9939	$237.99	$238.00	$238.00
7 purchase totals =	$1,253.74		$1,371.8746	$1,371.87	$1,371.90	$1,372.00