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	$234.72	4.658%	$245.6533	$245.65	$245.65	$245.70
Purchase #2	$241.85	7.737%	$260.5619	$260.56	$260.55	$260.60
Purchase #3	$91.65	4.291%	$95.5827	$95.58	$95.60	$95.60
Purchase #4	$40.42	12.852%	$45.6148	$45.61	$45.60	$45.60
Purchase #5	$199.37	12.105%	$223.5037	$223.50	$223.50	$223.50
Purchase #6	$135.34	4.687%	$141.6834	$141.68	$141.70	$141.70
Purchase #7	$59.59	13.350%	$67.5453	$67.55	$67.55	$67.50
7 purchase totals =	$1,002.94		$1,080.1451	$1,080.13	$1,080.15	$1,080.20