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	$226.98	5.165%	$238.7035	$238.70	$238.70	$238.70
Purchase #2	$37.61	4.307%	$39.2299	$39.23	$39.25	$39.20
Purchase #3	$233.80	3.243%	$241.3821	$241.38	$241.40	$241.40
Purchase #4	$154.36	10.659%	$170.8132	$170.81	$170.80	$170.80
Purchase #5	$237.66	10.454%	$262.505	$262.51	$262.50	$262.50
Purchase #6	$99.54	12.295%	$111.7784	$111.78	$111.80	$111.80
Purchase #7	$132.72	13.465%	$150.5907	$150.59	$150.60	$150.60
7 purchase totals =	$1,122.67		$1,215.0028	$1,215.00	$1,215.05	$1,215.00