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	$112.85	13.784%	$128.4052	$128.41	$128.40	$128.40
Purchase #2	$180.83	10.611%	$200.0179	$200.02	$200.00	$200.00
Purchase #3	$137.40	11.857%	$153.6915	$153.69	$153.70	$153.70
Purchase #4	$201.75	7.299%	$216.4757	$216.48	$216.50	$216.50
Purchase #5	$104.54	12.549%	$117.6587	$117.66	$117.65	$117.70
Purchase #6	$50.93	4.570%	$53.2575	$53.26	$53.25	$53.30
Purchase #7	$205.41	9.481%	$224.8849	$224.88	$224.90	$224.90
7 purchase totals =	$993.71		$1,094.3914	$1,094.40	$1,094.40	$1,094.50