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	$219.61	3.619%	$227.5577	$227.56	$227.55	$227.60
Purchase #2	$75.61	10.624%	$83.6428	$83.64	$83.65	$83.60
Purchase #3	$88.59	12.528%	$99.6886	$99.69	$99.70	$99.70
Purchase #4	$232.60	5.363%	$245.0743	$245.07	$245.05	$245.10
Purchase #5	$98.25	10.162%	$108.2342	$108.23	$108.25	$108.20
Purchase #6	$215.48	7.212%	$231.0204	$231.02	$231.00	$231.00
Purchase #7	$95.46	8.850%	$103.9082	$103.91	$103.90	$103.90
7 purchase totals =	$1,025.60		$1,099.1262	$1,099.12	$1,099.10	$1,099.10