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	$88.29	7.425%	$94.8455	$94.85	$94.85	$94.80
Purchase #2	$227.92	12.772%	$257.0299	$257.03	$257.05	$257.00
Purchase #3	$169.33	4.365%	$176.7213	$176.72	$176.70	$176.70
Purchase #4	$146.76	6.790%	$156.725	$156.73	$156.75	$156.70
Purchase #5	$244.47	7.325%	$262.3774	$262.38	$262.40	$262.40
Purchase #6	$216.36	3.245%	$223.3809	$223.38	$223.40	$223.40
Purchase #7	$25.93	13.655%	$29.4707	$29.47	$29.45	$29.50
7 purchase totals =	$1,119.06		$1,200.5507	$1,200.56	$1,200.60	$1,200.50