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	$184.40	13.263%	$208.857	$208.86	$208.85	$208.90
Purchase #2	$129.43	12.641%	$145.7912	$145.79	$145.80	$145.80
Purchase #3	$143.44	4.303%	$149.6122	$149.61	$149.60	$149.60
Purchase #4	$64.80	12.467%	$72.8786	$72.88	$72.90	$72.90
Purchase #5	$37.96	13.578%	$43.1142	$43.11	$43.10	$43.10
Purchase #6	$34.30	8.174%	$37.1037	$37.10	$37.10	$37.10
Purchase #7	$61.54	5.505%	$64.9278	$64.93	$64.95	$64.90
7 purchase totals =	$655.87		$722.2847	$722.28	$722.30	$722.30