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	$116.89	10.778%	$129.4884	$129.49	$129.50	$129.50
Purchase #2	$150.67	9.420%	$164.8631	$164.86	$164.85	$164.90
Purchase #3	$57.73	3.543%	$59.7754	$59.78	$59.80	$59.80
Purchase #4	$163.31	9.409%	$178.6758	$178.68	$178.70	$178.70
Purchase #5	$28.62	11.622%	$31.9462	$31.95	$31.95	$31.90
Purchase #6	$13.82	8.575%	$15.0051	$15.01	$15.00	$15.00
Purchase #7	$61.77	6.674%	$65.8925	$65.89	$65.90	$65.90
7 purchase totals =	$592.81		$645.6465	$645.66	$645.70	$645.70