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	$93.83	12.709%	$105.7549	$105.75	$105.75	$105.80
Purchase #2	$91.85	13.123%	$103.9035	$103.90	$103.90	$103.90
Purchase #3	$86.84	6.750%	$92.7017	$92.70	$92.70	$92.70
Purchase #4	$37.81	12.103%	$42.3861	$42.39	$42.40	$42.40
Purchase #5	$215.48	9.383%	$235.6985	$235.70	$235.70	$235.70
Purchase #6	$212.49	7.239%	$227.8722	$227.87	$227.85	$227.90
Purchase #7	$171.80	13.852%	$195.5977	$195.60	$195.60	$195.60
7 purchase totals =	$910.10		$1,003.9146	$1,003.91	$1,003.90	$1,004.00