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	$89.47	4.469%	$93.4684	$93.47	$93.45	$93.50
Purchase #2	$155.27	9.607%	$170.1868	$170.19	$170.20	$170.20
Purchase #3	$184.31	8.262%	$199.5377	$199.54	$199.55	$199.50
Purchase #4	$94.63	5.434%	$99.7722	$99.77	$99.75	$99.80
Purchase #5	$69.31	6.385%	$73.7354	$73.74	$73.75	$73.70
Purchase #6	$119.29	3.836%	$123.866	$123.87	$123.85	$123.90
Purchase #7	$95.71	4.790%	$100.2945	$100.29	$100.30	$100.30
7 purchase totals =	$807.99		$860.8610	$860.87	$860.85	$860.90