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	$113.80	8.228%	$123.1635	$123.16	$123.15	$123.20
Purchase #2	$9.48	6.292%	$10.0765	$10.08	$10.10	$10.10
Purchase #3	$233.75	3.713%	$242.4291	$242.43	$242.45	$242.40
Purchase #4	$81.59	5.211%	$85.8417	$85.84	$85.85	$85.80
Purchase #5	$90.32	4.533%	$94.4142	$94.41	$94.40	$94.40
Purchase #6	$68.75	11.611%	$76.7326	$76.73	$76.75	$76.70
Purchase #7	$163.72	13.231%	$185.3818	$185.38	$185.40	$185.40
7 purchase totals =	$761.41		$818.0394	$818.03	$818.10	$818.00