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	$111.37	6.369%	$118.4632	$118.46	$118.45	$118.50
Purchase #2	$136.46	7.195%	$146.2783	$146.28	$146.30	$146.30
Purchase #3	$213.47	12.319%	$239.7674	$239.77	$239.75	$239.80
Purchase #4	$99.44	6.576%	$105.9792	$105.98	$106.00	$106.00
Purchase #5	$134.28	5.389%	$141.5163	$141.52	$141.50	$141.50
Purchase #6	$90.46	13.634%	$102.7933	$102.79	$102.80	$102.80
Purchase #7	$137.66	10.300%	$151.839	$151.84	$151.85	$151.80
7 purchase totals =	$923.14		$1,006.6367	$1,006.64	$1,006.65	$1,006.70