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	$201.71	10.353%	$222.593	$222.59	$222.60	$222.60
Purchase #2	$95.77	12.593%	$107.8303	$107.83	$107.85	$107.80
Purchase #3	$237.94	3.493%	$246.2512	$246.25	$246.25	$246.30
Purchase #4	$84.82	11.148%	$94.2757	$94.28	$94.30	$94.30
Purchase #5	$129.85	11.790%	$145.1593	$145.16	$145.15	$145.20
Purchase #6	$39.60	7.492%	$42.5668	$42.57	$42.55	$42.60
Purchase #7	$137.96	7.856%	$148.7981	$148.80	$148.80	$148.80
7 purchase totals =	$927.65		$1,007.4744	$1,007.48	$1,007.50	$1,007.60