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	$149.59	4.111%	$155.7396	$155.74	$155.75	$155.70
Purchase #2	$136.73	11.556%	$152.5305	$152.53	$152.55	$152.50
Purchase #3	$80.69	7.105%	$86.423	$86.42	$86.40	$86.40
Purchase #4	$35.25	6.333%	$37.4824	$37.48	$37.50	$37.50
Purchase #5	$43.64	11.854%	$48.8131	$48.81	$48.80	$48.80
Purchase #6	$63.85	12.785%	$72.0132	$72.01	$72.00	$72.00
Purchase #7	$170.44	10.667%	$188.6208	$188.62	$188.60	$188.60
7 purchase totals =	$680.19		$741.6226	$741.61	$741.60	$741.50