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	$173.72	12.152%	$194.8305	$194.83	$194.85	$194.80
Purchase #2	$239.62	7.757%	$258.2073	$258.21	$258.20	$258.20
Purchase #3	$237.75	8.472%	$257.8922	$257.89	$257.90	$257.90
Purchase #4	$132.89	9.619%	$145.6727	$145.67	$145.65	$145.70
Purchase #5	$92.78	5.605%	$97.9803	$97.98	$98.00	$98.00
Purchase #6	$203.90	7.154%	$218.487	$218.49	$218.50	$218.50
Purchase #7	$78.40	5.625%	$82.81	$82.81	$82.80	$82.80
7 purchase totals =	$1,159.06		$1,255.8800	$1,255.88	$1,255.90	$1,255.90