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	$96.81	4.176%	$100.8528	$100.85	$100.85	$100.90
Purchase #2	$18.94	7.485%	$20.3577	$20.36	$20.35	$20.40
Purchase #3	$60.25	10.792%	$66.7522	$66.75	$66.75	$66.80
Purchase #4	$95.29	13.764%	$108.4057	$108.41	$108.40	$108.40
Purchase #5	$83.43	7.642%	$89.8057	$89.81	$89.80	$89.80
Purchase #6	$236.53	3.628%	$245.1113	$245.11	$245.10	$245.10
Purchase #7	$116.41	10.455%	$128.5807	$128.58	$128.60	$128.60
7 purchase totals =	$707.66		$759.8661	$759.87	$759.85	$760.00