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	$57.34	3.149%	$59.1456	$59.15	$59.15	$59.10
Purchase #2	$162.40	10.227%	$179.0086	$179.01	$179.00	$179.00
Purchase #3	$126.43	5.595%	$133.5038	$133.50	$133.50	$133.50
Purchase #4	$246.64	4.778%	$258.4245	$258.42	$258.40	$258.40
Purchase #5	$84.42	11.186%	$93.8632	$93.86	$93.85	$93.90
Purchase #6	$204.89	13.188%	$231.9109	$231.91	$231.90	$231.90
Purchase #7	$110.33	11.297%	$122.794	$122.79	$122.80	$122.80
7 purchase totals =	$992.45		$1,078.6506	$1,078.64	$1,078.60	$1,078.60