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	$151.39	10.211%	$166.8484	$166.85	$166.85	$166.80
Purchase #2	$81.40	7.377%	$87.4049	$87.40	$87.40	$87.40
Purchase #3	$40.51	4.843%	$42.4719	$42.47	$42.45	$42.50
Purchase #4	$31.39	12.315%	$35.2557	$35.26	$35.25	$35.30
Purchase #5	$86.55	10.610%	$95.733	$95.73	$95.75	$95.70
Purchase #6	$36.31	10.255%	$40.0336	$40.03	$40.05	$40.00
Purchase #7	$100.58	5.271%	$105.8816	$105.88	$105.90	$105.90
7 purchase totals =	$528.13		$573.6291	$573.62	$573.65	$573.60