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	$140.25	12.102%	$157.2231	$157.22	$157.20	$157.20
Purchase #2	$172.43	11.639%	$192.4991	$192.50	$192.50	$192.50
Purchase #3	$184.25	4.420%	$192.3939	$192.39	$192.40	$192.40
Purchase #4	$58.61	6.377%	$62.3476	$62.35	$62.35	$62.30
Purchase #5	$131.33	11.636%	$146.6116	$146.61	$146.60	$146.60
Purchase #6	$195.52	4.104%	$203.5441	$203.54	$203.55	$203.50
Purchase #7	$58.38	6.446%	$62.1432	$62.14	$62.15	$62.10
7 purchase totals =	$940.77		$1,016.7626	$1,016.75	$1,016.75	$1,016.60