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	$117.48	12.377%	$132.0205	$132.02	$132.00	$132.00
Purchase #2	$170.58	7.512%	$183.394	$183.39	$183.40	$183.40
Purchase #3	$107.62	3.345%	$111.2199	$111.22	$111.20	$111.20
Purchase #4	$243.85	9.379%	$266.7207	$266.72	$266.70	$266.70
Purchase #5	$219.90	13.436%	$249.4458	$249.45	$249.45	$249.40
Purchase #6	$218.25	13.122%	$246.8888	$246.89	$246.90	$246.90
Purchase #7	$59.32	10.214%	$65.3789	$65.38	$65.40	$65.40
7 purchase totals =	$1,137.00		$1,255.0686	$1,255.07	$1,255.05	$1,255.00