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	$39.85	13.408%	$45.1931	$45.19	$45.20	$45.20
Purchase #2	$121.72	4.665%	$127.3982	$127.40	$127.40	$127.40
Purchase #3	$140.81	7.805%	$151.8002	$151.80	$151.80	$151.80
Purchase #4	$137.84	3.544%	$142.725	$142.73	$142.75	$142.70
Purchase #5	$80.39	11.684%	$89.7828	$89.78	$89.80	$89.80
Purchase #6	$152.86	9.235%	$166.9766	$166.98	$167.00	$167.00
Purchase #7	$223.98	6.105%	$237.654	$237.65	$237.65	$237.70
7 purchase totals =	$897.45		$961.5299	$961.53	$961.60	$961.60