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	$245.66	10.346%	$271.076	$271.08	$271.10	$271.10
Purchase #2	$20.56	3.313%	$21.2412	$21.24	$21.25	$21.20
Purchase #3	$29.42	12.162%	$32.9981	$33.00	$33.00	$33.00
Purchase #4	$41.32	13.506%	$46.9007	$46.90	$46.90	$46.90
Purchase #5	$21.80	12.447%	$24.5134	$24.51	$24.50	$24.50
Purchase #6	$154.90	3.795%	$160.7785	$160.78	$160.80	$160.80
Purchase #7	$98.61	7.141%	$105.6517	$105.65	$105.65	$105.70
7 purchase totals =	$612.27		$663.1596	$663.16	$663.20	$663.20