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	$94.48	9.652%	$103.5992	$103.60	$103.60	$103.60
Purchase #2	$190.34	10.460%	$210.2496	$210.25	$210.25	$210.20
Purchase #3	$59.36	5.267%	$62.4865	$62.49	$62.50	$62.50
Purchase #4	$52.97	12.283%	$59.4763	$59.48	$59.50	$59.50
Purchase #5	$10.60	7.257%	$11.3692	$11.37	$11.35	$11.40
Purchase #6	$58.70	6.772%	$62.6752	$62.68	$62.70	$62.70
Purchase #7	$215.66	11.761%	$241.0238	$241.02	$241.00	$241.00
7 purchase totals =	$682.11		$750.8798	$750.89	$750.90	$750.90