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	$218.53	11.481%	$243.6194	$243.62	$243.60	$243.60
Purchase #2	$183.28	13.760%	$208.4993	$208.50	$208.50	$208.50
Purchase #3	$213.78	13.549%	$242.7451	$242.75	$242.75	$242.70
Purchase #4	$172.50	11.578%	$192.4721	$192.47	$192.45	$192.50
Purchase #5	$89.42	8.324%	$96.8633	$96.86	$96.85	$96.90
Purchase #6	$167.46	3.134%	$172.7082	$172.71	$172.70	$172.70
Purchase #7	$178.55	4.247%	$186.133	$186.13	$186.15	$186.10
7 purchase totals =	$1,223.52		$1,343.0404	$1,343.04	$1,343.00	$1,343.00