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	$47.38	9.134%	$51.7077	$51.71	$51.70	$51.70
Purchase #2	$30.29	5.179%	$31.8587	$31.86	$31.85	$31.90
Purchase #3	$35.83	12.829%	$40.4266	$40.43	$40.45	$40.40
Purchase #4	$194.71	8.207%	$210.6898	$210.69	$210.70	$210.70
Purchase #5	$195.34	12.563%	$219.8806	$219.88	$219.90	$219.90
Purchase #6	$31.29	13.534%	$35.5248	$35.52	$35.50	$35.50
Purchase #7	$227.47	6.285%	$241.7665	$241.77	$241.75	$241.80
7 purchase totals =	$762.31		$831.8547	$831.86	$831.85	$831.90