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	$56.69	12.209%	$63.6113	$63.61	$63.60	$63.60
Purchase #2	$183.83	11.846%	$205.6065	$205.61	$205.60	$205.60
Purchase #3	$68.34	5.143%	$71.8547	$71.85	$71.85	$71.90
Purchase #4	$143.58	11.175%	$159.6251	$159.63	$159.65	$159.60
Purchase #5	$134.74	11.642%	$150.4264	$150.43	$150.45	$150.40
Purchase #6	$101.77	8.761%	$110.6861	$110.69	$110.70	$110.70
Purchase #7	$139.83	11.635%	$156.0992	$156.10	$156.10	$156.10
7 purchase totals =	$828.78		$917.9093	$917.92	$917.95	$917.90