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	$153.79	5.725%	$162.5945	$162.59	$162.60	$162.60
Purchase #2	$46.39	3.770%	$48.1389	$48.14	$48.15	$48.10
Purchase #3	$75.53	13.604%	$85.8051	$85.81	$85.80	$85.80
Purchase #4	$149.76	3.644%	$155.2173	$155.22	$155.20	$155.20
Purchase #5	$162.53	5.630%	$171.6804	$171.68	$171.70	$171.70
Purchase #6	$140.51	13.491%	$159.4662	$159.47	$159.45	$159.50
Purchase #7	$72.97	7.305%	$78.3005	$78.30	$78.30	$78.30
7 purchase totals =	$801.48		$861.2029	$861.21	$861.20	$861.20