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	$111.27	5.509%	$117.3999	$117.40	$117.40	$117.40
Purchase #2	$129.27	7.763%	$139.3052	$139.31	$139.30	$139.30
Purchase #3	$216.55	6.704%	$231.0675	$231.07	$231.05	$231.10
Purchase #4	$219.48	11.143%	$243.9367	$243.94	$243.95	$243.90
Purchase #5	$186.32	7.798%	$200.8492	$200.85	$200.85	$200.80
Purchase #6	$206.88	7.532%	$222.4622	$222.46	$222.45	$222.50
Purchase #7	$127.83	5.107%	$134.3583	$134.36	$134.35	$134.40
7 purchase totals =	$1,197.60		$1,289.3790	$1,289.39	$1,289.35	$1,289.40