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	$222.66	9.844%	$244.5787	$244.58	$244.60	$244.60
Purchase #2	$96.64	3.593%	$100.1123	$100.11	$100.10	$100.10
Purchase #3	$144.95	12.425%	$162.96	$162.96	$162.95	$163.00
Purchase #4	$158.63	4.431%	$165.6589	$165.66	$165.65	$165.70
Purchase #5	$15.35	3.215%	$15.8435	$15.84	$15.85	$15.80
Purchase #6	$88.73	10.311%	$97.879	$97.88	$97.90	$97.90
Purchase #7	$216.63	3.333%	$223.8503	$223.85	$223.85	$223.90
7 purchase totals =	$943.59		$1,010.8827	$1,010.88	$1,010.90	$1,011.00