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	$222.34	6.759%	$237.368	$237.37	$237.35	$237.40
Purchase #2	$217.57	9.866%	$239.0355	$239.04	$239.05	$239.00
Purchase #3	$151.87	13.434%	$172.2722	$172.27	$172.25	$172.30
Purchase #4	$71.83	7.464%	$77.1914	$77.19	$77.20	$77.20
Purchase #5	$113.64	4.820%	$119.1174	$119.12	$119.10	$119.10
Purchase #6	$155.39	8.477%	$168.5624	$168.56	$168.55	$168.60
Purchase #7	$66.67	7.846%	$71.9009	$71.90	$71.90	$71.90
7 purchase totals =	$999.31		$1,085.4478	$1,085.45	$1,085.40	$1,085.50