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	$50.73	6.189%	$53.8697	$53.87	$53.85	$53.90
Purchase #2	$82.94	6.600%	$88.414	$88.41	$88.40	$88.40
Purchase #3	$94.68	3.626%	$98.1131	$98.11	$98.10	$98.10
Purchase #4	$35.28	10.230%	$38.8891	$38.89	$38.90	$38.90
Purchase #5	$155.85	4.330%	$162.5983	$162.60	$162.60	$162.60
Purchase #6	$105.42	11.146%	$117.1701	$117.17	$117.15	$117.20
Purchase #7	$210.44	8.116%	$227.5193	$227.52	$227.50	$227.50
7 purchase totals =	$735.34		$786.5736	$786.57	$786.50	$786.60