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	$138.42	10.494%	$152.9458	$152.95	$152.95	$152.90
Purchase #2	$162.52	12.394%	$182.6627	$182.66	$182.65	$182.70
Purchase #3	$113.30	13.143%	$128.191	$128.19	$128.20	$128.20
Purchase #4	$19.95	3.196%	$20.5876	$20.59	$20.60	$20.60
Purchase #5	$147.45	7.454%	$158.4409	$158.44	$158.45	$158.40
Purchase #6	$157.79	6.561%	$168.1426	$168.14	$168.15	$168.10
Purchase #7	$45.47	6.693%	$48.5133	$48.51	$48.50	$48.50
7 purchase totals =	$784.90		$859.4839	$859.48	$859.50	$859.40