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	$47.69	4.644%	$49.9047	$49.90	$49.90	$49.90
Purchase #2	$155.70	7.831%	$167.8929	$167.89	$167.90	$167.90
Purchase #3	$173.95	11.813%	$194.4987	$194.50	$194.50	$194.50
Purchase #4	$194.61	13.228%	$220.353	$220.35	$220.35	$220.40
Purchase #5	$214.95	5.853%	$227.531	$227.53	$227.55	$227.50
Purchase #6	$213.75	4.705%	$223.8069	$223.81	$223.80	$223.80
Purchase #7	$53.39	4.274%	$55.6719	$55.67	$55.65	$55.70
7 purchase totals =	$1,054.04		$1,139.6591	$1,139.65	$1,139.65	$1,139.70