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	$168.64	13.152%	$190.8195	$190.82	$190.80	$190.80
Purchase #2	$163.63	3.220%	$168.8989	$168.90	$168.90	$168.90
Purchase #3	$87.53	8.557%	$95.0199	$95.02	$95.00	$95.00
Purchase #4	$188.40	9.592%	$206.4713	$206.47	$206.45	$206.50
Purchase #5	$105.74	13.268%	$119.7696	$119.77	$119.75	$119.80
Purchase #6	$40.30	13.782%	$45.8541	$45.85	$45.85	$45.90
Purchase #7	$145.62	4.224%	$151.771	$151.77	$151.75	$151.80
7 purchase totals =	$899.86		$978.6043	$978.60	$978.50	$978.70