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	$203.84	10.328%	$224.8926	$224.89	$224.90	$224.90
Purchase #2	$78.86	4.827%	$82.6666	$82.67	$82.65	$82.70
Purchase #3	$130.84	6.122%	$138.85	$138.85	$138.85	$138.90
Purchase #4	$92.31	13.209%	$104.5032	$104.50	$104.50	$104.50
Purchase #5	$146.69	8.128%	$158.613	$158.61	$158.60	$158.60
Purchase #6	$209.50	4.395%	$218.7075	$218.71	$218.70	$218.70
Purchase #7	$162.61	8.863%	$177.0221	$177.02	$177.00	$177.00
7 purchase totals =	$1,024.65		$1,105.2550	$1,105.25	$1,105.20	$1,105.30