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	$113.76	8.299%	$123.2009	$123.20	$123.20	$123.20
Purchase #2	$11.97	12.745%	$13.4956	$13.50	$13.50	$13.50
Purchase #3	$62.70	7.169%	$67.195	$67.20	$67.20	$67.20
Purchase #4	$56.28	3.466%	$58.2307	$58.23	$58.25	$58.20
Purchase #5	$73.81	11.799%	$82.5188	$82.52	$82.50	$82.50
Purchase #6	$172.82	10.456%	$190.8901	$190.89	$190.90	$190.90
Purchase #7	$22.83	7.558%	$24.5555	$24.56	$24.55	$24.60
7 purchase totals =	$514.17		$560.0866	$560.10	$560.10	$560.10