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	$160.57	7.428%	$172.4971	$172.50	$172.50	$172.50
Purchase #2	$78.27	6.702%	$83.5157	$83.52	$83.50	$83.50
Purchase #3	$224.82	7.411%	$241.4814	$241.48	$241.50	$241.50
Purchase #4	$207.38	8.194%	$224.3727	$224.37	$224.35	$224.40
Purchase #5	$208.56	5.517%	$220.0663	$220.07	$220.05	$220.10
Purchase #6	$179.33	6.159%	$190.3749	$190.37	$190.35	$190.40
Purchase #7	$189.31	6.492%	$201.6	$201.60	$201.60	$201.60
7 purchase totals =	$1,248.24		$1,333.9081	$1,333.91	$1,333.85	$1,334.00