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	$227.87	12.587%	$256.552	$256.55	$256.55	$256.60
Purchase #2	$69.52	4.686%	$72.7777	$72.78	$72.80	$72.80
Purchase #3	$231.97	4.536%	$242.4922	$242.49	$242.50	$242.50
Purchase #4	$248.36	8.505%	$269.483	$269.48	$269.50	$269.50
Purchase #5	$225.68	13.229%	$255.5352	$255.54	$255.55	$255.50
Purchase #6	$143.58	5.751%	$151.8373	$151.84	$151.85	$151.80
Purchase #7	$161.91	4.577%	$169.3206	$169.32	$169.30	$169.30
7 purchase totals =	$1,308.89		$1,417.9980	$1,418.00	$1,418.05	$1,418.00