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	$125.94	8.863%	$137.1021	$137.10	$137.10	$137.10
Purchase #2	$101.46	5.384%	$106.9226	$106.92	$106.90	$106.90
Purchase #3	$227.81	11.747%	$254.5708	$254.57	$254.55	$254.60
Purchase #4	$107.34	3.757%	$111.3728	$111.37	$111.35	$111.40
Purchase #5	$104.54	12.864%	$117.988	$117.99	$118.00	$118.00
Purchase #6	$155.60	4.640%	$162.8198	$162.82	$162.80	$162.80
Purchase #7	$201.38	10.705%	$222.9377	$222.94	$222.95	$222.90
7 purchase totals =	$1,024.07		$1,113.7138	$1,113.71	$1,113.65	$1,113.70