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	$137.60	3.595%	$142.5467	$142.55	$142.55	$142.50
Purchase #2	$37.48	3.769%	$38.8926	$38.89	$38.90	$38.90
Purchase #3	$188.56	12.397%	$211.9358	$211.94	$211.95	$211.90
Purchase #4	$157.90	9.128%	$172.3131	$172.31	$172.30	$172.30
Purchase #5	$140.52	13.841%	$159.9694	$159.97	$159.95	$160.00
Purchase #6	$86.45	7.112%	$92.5983	$92.60	$92.60	$92.60
Purchase #7	$157.57	4.384%	$164.4779	$164.48	$164.50	$164.50
7 purchase totals =	$906.08		$982.7338	$982.74	$982.75	$982.70