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	$138.42	13.427%	$157.0057	$157.01	$157.00	$157.00
Purchase #2	$193.37	11.120%	$214.8727	$214.87	$214.85	$214.90
Purchase #3	$142.45	7.185%	$152.685	$152.69	$152.70	$152.70
Purchase #4	$238.46	7.152%	$255.5147	$255.51	$255.50	$255.50
Purchase #5	$157.40	12.853%	$177.6306	$177.63	$177.65	$177.60
Purchase #6	$154.83	13.604%	$175.8931	$175.89	$175.90	$175.90
Purchase #7	$152.47	9.772%	$167.3694	$167.37	$167.35	$167.40
7 purchase totals =	$1,177.40		$1,300.9712	$1,300.97	$1,300.95	$1,301.00