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	$99.76	13.465%	$113.1927	$113.19	$113.20	$113.20
Purchase #2	$67.59	13.172%	$76.493	$76.49	$76.50	$76.50
Purchase #3	$201.97	6.695%	$215.4919	$215.49	$215.50	$215.50
Purchase #4	$57.50	4.198%	$59.9139	$59.91	$59.90	$59.90
Purchase #5	$187.59	11.540%	$209.2379	$209.24	$209.25	$209.20
Purchase #6	$224.95	6.697%	$240.0149	$240.01	$240.00	$240.00
Purchase #7	$88.40	7.314%	$94.8656	$94.87	$94.85	$94.90
7 purchase totals =	$927.76		$1,009.2099	$1,009.20	$1,009.20	$1,009.20