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	$197.85	9.775%	$217.1898	$217.19	$217.20	$217.20
Purchase #2	$145.57	4.470%	$152.077	$152.08	$152.10	$152.10
Purchase #3	$202.50	9.324%	$221.3811	$221.38	$221.40	$221.40
Purchase #4	$40.38	11.796%	$45.1432	$45.14	$45.15	$45.10
Purchase #5	$194.35	11.266%	$216.2455	$216.25	$216.25	$216.20
Purchase #6	$162.93	13.563%	$185.0282	$185.03	$185.05	$185.00
Purchase #7	$64.65	4.427%	$67.5121	$67.51	$67.50	$67.50
7 purchase totals =	$1,008.23		$1,104.5769	$1,104.58	$1,104.65	$1,104.50