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	$142.97	3.352%	$147.7624	$147.76	$147.75	$147.80
Purchase #2	$65.31	11.353%	$72.7246	$72.72	$72.70	$72.70
Purchase #3	$91.42	8.224%	$98.9384	$98.94	$98.95	$98.90
Purchase #4	$40.87	10.211%	$45.0432	$45.04	$45.05	$45.00
Purchase #5	$48.58	7.411%	$52.1803	$52.18	$52.20	$52.20
Purchase #6	$75.89	3.624%	$78.6403	$78.64	$78.65	$78.60
Purchase #7	$166.34	11.545%	$185.544	$185.54	$185.55	$185.50
7 purchase totals =	$631.38		$680.8332	$680.82	$680.85	$680.70