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	$217.92	5.240%	$229.339	$229.34	$229.35	$229.30
Purchase #2	$133.90	12.389%	$150.4889	$150.49	$150.50	$150.50
Purchase #3	$218.99	3.784%	$227.2766	$227.28	$227.30	$227.30
Purchase #4	$179.88	3.473%	$186.1272	$186.13	$186.15	$186.10
Purchase #5	$230.37	3.761%	$239.0342	$239.03	$239.05	$239.00
Purchase #6	$81.55	11.451%	$90.8883	$90.89	$90.90	$90.90
Purchase #7	$101.73	3.611%	$105.4035	$105.40	$105.40	$105.40
7 purchase totals =	$1,164.34		$1,228.5577	$1,228.56	$1,228.65	$1,228.50