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	$132.72	11.808%	$148.3916	$148.39	$148.40	$148.40
Purchase #2	$132.37	4.105%	$137.8038	$137.80	$137.80	$137.80
Purchase #3	$73.33	3.657%	$76.0117	$76.01	$76.00	$76.00
Purchase #4	$166.58	11.300%	$185.4035	$185.40	$185.40	$185.40
Purchase #5	$202.69	6.771%	$216.4141	$216.41	$216.40	$216.40
Purchase #6	$35.54	4.800%	$37.2459	$37.25	$37.25	$37.20
Purchase #7	$62.78	4.531%	$65.6246	$65.62	$65.60	$65.60
7 purchase totals =	$806.01		$866.8952	$866.88	$866.85	$866.80