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	$173.89	6.741%	$185.6119	$185.61	$185.60	$185.60
Purchase #2	$63.93	5.680%	$67.5612	$67.56	$67.55	$67.60
Purchase #3	$34.40	3.781%	$35.7007	$35.70	$35.70	$35.70
Purchase #4	$232.50	12.408%	$261.3486	$261.35	$261.35	$261.30
Purchase #5	$153.89	11.859%	$172.1398	$172.14	$172.15	$172.10
Purchase #6	$66.63	9.777%	$73.1444	$73.14	$73.15	$73.10
Purchase #7	$210.85	4.621%	$220.5934	$220.59	$220.60	$220.60
7 purchase totals =	$936.09		$1,016.1000	$1,016.09	$1,016.10	$1,016.00