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	$210.37	6.169%	$223.3477	$223.35	$223.35	$223.30
Purchase #2	$124.88	11.764%	$139.5709	$139.57	$139.55	$139.60
Purchase #3	$64.48	3.157%	$66.5156	$66.52	$66.50	$66.50
Purchase #4	$197.82	5.361%	$208.4251	$208.43	$208.45	$208.40
Purchase #5	$142.32	4.259%	$148.3814	$148.38	$148.40	$148.40
Purchase #6	$59.87	5.485%	$63.1539	$63.15	$63.15	$63.20
Purchase #7	$196.93	12.553%	$221.6506	$221.65	$221.65	$221.70
7 purchase totals =	$996.67		$1,071.0452	$1,071.05	$1,071.05	$1,071.10