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	$124.76	6.308%	$132.6299	$132.63	$132.65	$132.60
Purchase #2	$91.90	3.802%	$95.394	$95.39	$95.40	$95.40
Purchase #3	$33.31	3.555%	$34.4942	$34.49	$34.50	$34.50
Purchase #4	$97.77	7.304%	$104.9111	$104.91	$104.90	$104.90
Purchase #5	$45.96	12.475%	$51.6935	$51.69	$51.70	$51.70
Purchase #6	$200.41	13.575%	$227.6157	$227.62	$227.60	$227.60
Purchase #7	$199.39	13.105%	$225.5201	$225.52	$225.50	$225.50
7 purchase totals =	$793.50		$872.2585	$872.25	$872.25	$872.20