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	$205.54	10.674%	$227.4793	$227.48	$227.50	$227.50
Purchase #2	$42.47	12.105%	$47.611	$47.61	$47.60	$47.60
Purchase #3	$146.89	11.374%	$163.5973	$163.60	$163.60	$163.60
Purchase #4	$197.80	11.303%	$220.1573	$220.16	$220.15	$220.20
Purchase #5	$73.58	12.668%	$82.9011	$82.90	$82.90	$82.90
Purchase #6	$75.37	4.622%	$78.8536	$78.85	$78.85	$78.90
Purchase #7	$67.88	8.266%	$73.491	$73.49	$73.50	$73.50
7 purchase totals =	$809.53		$894.0906	$894.09	$894.10	$894.20