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	$216.30	7.476%	$232.4706	$232.47	$232.45	$232.50
Purchase #2	$190.79	11.732%	$213.1735	$213.17	$213.15	$213.20
Purchase #3	$132.41	13.314%	$150.0391	$150.04	$150.05	$150.00
Purchase #4	$72.82	8.291%	$78.8575	$78.86	$78.85	$78.90
Purchase #5	$35.47	11.272%	$39.4682	$39.47	$39.45	$39.50
Purchase #6	$70.45	11.264%	$78.3855	$78.39	$78.40	$78.40
Purchase #7	$92.77	12.790%	$104.6353	$104.64	$104.65	$104.60
7 purchase totals =	$811.01		$897.0297	$897.04	$897.00	$897.10