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	$8.82	13.855%	$10.042	$10.04	$10.05	$10.00
Purchase #2	$119.30	9.262%	$130.3496	$130.35	$130.35	$130.30
Purchase #3	$36.46	3.351%	$37.6818	$37.68	$37.70	$37.70
Purchase #4	$16.32	12.257%	$18.3203	$18.32	$18.30	$18.30
Purchase #5	$64.65	4.577%	$67.609	$67.61	$67.60	$67.60
Purchase #6	$93.26	8.661%	$101.3372	$101.34	$101.35	$101.30
Purchase #7	$60.30	6.493%	$64.2153	$64.22	$64.20	$64.20
7 purchase totals =	$399.11		$429.5552	$429.56	$429.55	$429.40