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	$107.86	5.191%	$113.459	$113.46	$113.45	$113.50
Purchase #2	$37.95	4.344%	$39.5985	$39.60	$39.60	$39.60
Purchase #3	$196.65	10.496%	$217.2904	$217.29	$217.30	$217.30
Purchase #4	$23.71	4.680%	$24.8196	$24.82	$24.80	$24.80
Purchase #5	$53.72	10.803%	$59.5234	$59.52	$59.50	$59.50
Purchase #6	$152.40	10.381%	$168.2206	$168.22	$168.20	$168.20
Purchase #7	$152.54	10.459%	$168.4942	$168.49	$168.50	$168.50
7 purchase totals =	$724.83		$791.4057	$791.40	$791.35	$791.40