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	$246.61	10.490%	$272.4794	$272.48	$272.50	$272.50
Purchase #2	$188.46	4.501%	$196.9426	$196.94	$196.95	$196.90
Purchase #3	$65.62	10.577%	$72.5606	$72.56	$72.55	$72.60
Purchase #4	$9.98	10.228%	$11.0008	$11.00	$11.00	$11.00
Purchase #5	$84.86	4.433%	$88.6218	$88.62	$88.60	$88.60
Purchase #6	$192.66	3.380%	$199.1719	$199.17	$199.15	$199.20
Purchase #7	$205.30	9.495%	$224.7932	$224.79	$224.80	$224.80
7 purchase totals =	$993.49		$1,065.5703	$1,065.56	$1,065.55	$1,065.60