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	$222.85	10.211%	$245.6052	$245.61	$245.60	$245.60
Purchase #2	$81.83	8.387%	$88.6931	$88.69	$88.70	$88.70
Purchase #3	$141.47	12.148%	$158.6558	$158.66	$158.65	$158.70
Purchase #4	$215.32	5.712%	$227.6191	$227.62	$227.60	$227.60
Purchase #5	$128.39	13.681%	$145.955	$145.96	$145.95	$146.00
Purchase #6	$128.28	12.143%	$143.857	$143.86	$143.85	$143.90
Purchase #7	$238.31	10.685%	$263.7734	$263.77	$263.75	$263.80
7 purchase totals =	$1,156.45		$1,274.1586	$1,274.17	$1,274.10	$1,274.30