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	$141.81	3.655%	$146.9932	$146.99	$147.00	$147.00
Purchase #2	$143.43	5.545%	$151.3832	$151.38	$151.40	$151.40
Purchase #3	$114.43	11.571%	$127.6707	$127.67	$127.65	$127.70
Purchase #4	$135.53	4.515%	$141.6492	$141.65	$141.65	$141.60
Purchase #5	$222.83	12.506%	$250.6971	$250.70	$250.70	$250.70
Purchase #6	$107.59	3.551%	$111.4105	$111.41	$111.40	$111.40
Purchase #7	$168.45	10.309%	$185.8155	$185.82	$185.80	$185.80
7 purchase totals =	$1,034.07		$1,115.6194	$1,115.62	$1,115.60	$1,115.60