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	$167.77	9.728%	$184.0907	$184.09	$184.10	$184.10
Purchase #2	$25.87	4.766%	$27.103	$27.10	$27.10	$27.10
Purchase #3	$236.31	4.390%	$246.684	$246.68	$246.70	$246.70
Purchase #4	$199.32	5.310%	$209.9039	$209.90	$209.90	$209.90
Purchase #5	$200.49	8.695%	$217.9226	$217.92	$217.90	$217.90
Purchase #6	$72.42	12.692%	$81.6115	$81.61	$81.60	$81.60
Purchase #7	$180.48	9.124%	$196.947	$196.95	$196.95	$196.90
7 purchase totals =	$1,082.66		$1,164.2627	$1,164.25	$1,164.25	$1,164.20