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	$184.62	8.488%	$200.2905	$200.29	$200.30	$200.30
Purchase #2	$235.87	5.153%	$248.0244	$248.02	$248.00	$248.00
Purchase #3	$203.51	7.405%	$218.5799	$218.58	$218.60	$218.60
Purchase #4	$228.58	13.508%	$259.4566	$259.46	$259.45	$259.50
Purchase #5	$197.46	7.556%	$212.3801	$212.38	$212.40	$212.40
Purchase #6	$74.56	4.634%	$78.0151	$78.02	$78.00	$78.00
Purchase #7	$245.53	4.200%	$255.8423	$255.84	$255.85	$255.80
7 purchase totals =	$1,370.13		$1,472.5889	$1,472.59	$1,472.60	$1,472.60