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	$193.67	11.787%	$216.4979	$216.50	$216.50	$216.50
Purchase #2	$190.77	13.861%	$217.2126	$217.21	$217.20	$217.20
Purchase #3	$84.56	7.186%	$90.6365	$90.64	$90.65	$90.60
Purchase #4	$142.34	13.753%	$161.916	$161.92	$161.90	$161.90
Purchase #5	$154.87	10.790%	$171.5805	$171.58	$171.60	$171.60
Purchase #6	$151.93	4.294%	$158.4539	$158.45	$158.45	$158.50
Purchase #7	$94.68	13.284%	$107.2573	$107.26	$107.25	$107.30
7 purchase totals =	$1,012.82		$1,123.5547	$1,123.56	$1,123.55	$1,123.60