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	$131.79	12.219%	$147.8934	$147.89	$147.90	$147.90
Purchase #2	$130.31	13.725%	$148.195	$148.20	$148.20	$148.20
Purchase #3	$43.95	6.821%	$46.9478	$46.95	$46.95	$46.90
Purchase #4	$92.62	10.166%	$102.0357	$102.04	$102.05	$102.00
Purchase #5	$177.34	8.189%	$191.8624	$191.86	$191.85	$191.90
Purchase #6	$94.88	12.251%	$106.5037	$106.50	$106.50	$106.50
Purchase #7	$38.58	11.228%	$42.9118	$42.91	$42.90	$42.90
7 purchase totals =	$709.47		$786.3498	$786.35	$786.35	$786.30