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	$98.83	4.839%	$103.6124	$103.61	$103.60	$103.60
Purchase #2	$70.63	4.554%	$73.8465	$73.85	$73.85	$73.80
Purchase #3	$44.79	3.699%	$46.4468	$46.45	$46.45	$46.40
Purchase #4	$221.92	4.660%	$232.2615	$232.26	$232.25	$232.30
Purchase #5	$65.74	8.712%	$71.4673	$71.47	$71.45	$71.50
Purchase #6	$159.82	8.567%	$173.5118	$173.51	$173.50	$173.50
Purchase #7	$135.52	10.730%	$150.0613	$150.06	$150.05	$150.10
7 purchase totals =	$797.25		$851.2076	$851.21	$851.15	$851.20