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	$52.56	13.148%	$59.4706	$59.47	$59.45	$59.50
Purchase #2	$195.92	5.522%	$206.7387	$206.74	$206.75	$206.70
Purchase #3	$114.66	5.119%	$120.5294	$120.53	$120.55	$120.50
Purchase #4	$29.60	13.213%	$33.511	$33.51	$33.50	$33.50
Purchase #5	$140.96	9.495%	$154.3442	$154.34	$154.35	$154.30
Purchase #6	$37.40	8.302%	$40.5049	$40.50	$40.50	$40.50
Purchase #7	$121.42	13.160%	$137.3989	$137.40	$137.40	$137.40
7 purchase totals =	$692.52		$752.4977	$752.49	$752.50	$752.40