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	$55.62	7.365%	$59.7164	$59.72	$59.70	$59.70
Purchase #2	$72.60	12.422%	$81.6184	$81.62	$81.60	$81.60
Purchase #3	$124.50	5.133%	$130.8906	$130.89	$130.90	$130.90
Purchase #4	$215.61	4.802%	$225.9636	$225.96	$225.95	$226.00
Purchase #5	$222.34	7.337%	$238.6531	$238.65	$238.65	$238.70
Purchase #6	$157.69	9.247%	$172.2716	$172.27	$172.25	$172.30
Purchase #7	$5.37	10.635%	$5.9411	$5.94	$5.95	$5.90
7 purchase totals =	$853.73		$915.0548	$915.05	$915.00	$915.10