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	$157.32	8.853%	$171.2475	$171.25	$171.25	$171.20
Purchase #2	$104.29	12.311%	$117.1291	$117.13	$117.15	$117.10
Purchase #3	$110.64	11.721%	$123.6081	$123.61	$123.60	$123.60
Purchase #4	$125.94	6.129%	$133.6589	$133.66	$133.65	$133.70
Purchase #5	$78.69	6.149%	$83.5286	$83.53	$83.55	$83.50
Purchase #6	$208.96	12.275%	$234.6098	$234.61	$234.60	$234.60
Purchase #7	$211.68	4.553%	$221.3178	$221.32	$221.30	$221.30
7 purchase totals =	$997.52		$1,085.0998	$1,085.11	$1,085.10	$1,085.00