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	$134.68	13.316%	$152.614	$152.61	$152.60	$152.60
Purchase #2	$41.91	6.823%	$44.7695	$44.77	$44.75	$44.80
Purchase #3	$43.90	4.656%	$45.944	$45.94	$45.95	$45.90
Purchase #4	$48.40	4.821%	$50.7334	$50.73	$50.75	$50.70
Purchase #5	$90.61	12.446%	$101.8873	$101.89	$101.90	$101.90
Purchase #6	$98.37	6.102%	$104.3725	$104.37	$104.35	$104.40
Purchase #7	$113.47	3.135%	$117.0273	$117.03	$117.05	$117.00
7 purchase totals =	$571.34		$617.3480	$617.34	$617.35	$617.30