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	$219.73	8.794%	$239.0531	$239.05	$239.05	$239.10
Purchase #2	$123.33	13.433%	$139.8969	$139.90	$139.90	$139.90
Purchase #3	$179.30	11.785%	$200.4305	$200.43	$200.45	$200.40
Purchase #4	$94.87	6.322%	$100.8677	$100.87	$100.85	$100.90
Purchase #5	$44.73	12.825%	$50.4666	$50.47	$50.45	$50.50
Purchase #6	$170.45	7.729%	$183.6241	$183.62	$183.60	$183.60
Purchase #7	$111.52	8.700%	$121.2222	$121.22	$121.20	$121.20
7 purchase totals =	$943.93		$1,035.5611	$1,035.56	$1,035.50	$1,035.60