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	$116.58	12.320%	$130.9427	$130.94	$130.95	$130.90
Purchase #2	$76.76	10.758%	$85.0178	$85.02	$85.00	$85.00
Purchase #3	$52.64	7.382%	$56.5259	$56.53	$56.55	$56.50
Purchase #4	$125.54	5.795%	$132.815	$132.82	$132.80	$132.80
Purchase #5	$190.42	10.169%	$209.7838	$209.78	$209.80	$209.80
Purchase #6	$243.48	12.213%	$273.2162	$273.22	$273.20	$273.20
Purchase #7	$36.88	8.603%	$40.0528	$40.05	$40.05	$40.10
7 purchase totals =	$842.30		$928.3542	$928.36	$928.35	$928.30