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	$227.69	7.446%	$244.6438	$244.64	$244.65	$244.60
Purchase #2	$154.45	13.312%	$175.0104	$175.01	$175.00	$175.00
Purchase #3	$59.83	4.620%	$62.5941	$62.59	$62.60	$62.60
Purchase #4	$246.60	13.188%	$279.1216	$279.12	$279.10	$279.10
Purchase #5	$210.69	5.651%	$222.5961	$222.60	$222.60	$222.60
Purchase #6	$169.96	6.549%	$181.0907	$181.09	$181.10	$181.10
Purchase #7	$5.82	5.298%	$6.1283	$6.13	$6.15	$6.10
7 purchase totals =	$1,075.04		$1,171.1850	$1,171.18	$1,171.20	$1,171.10