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	$190.35	9.657%	$208.7321	$208.73	$208.75	$208.70
Purchase #2	$45.38	13.420%	$51.47	$51.47	$51.45	$51.50
Purchase #3	$105.85	3.174%	$109.2097	$109.21	$109.20	$109.20
Purchase #4	$120.79	11.257%	$134.3873	$134.39	$134.40	$134.40
Purchase #5	$42.56	7.134%	$45.5962	$45.60	$45.60	$45.60
Purchase #6	$139.25	13.172%	$157.592	$157.59	$157.60	$157.60
Purchase #7	$56.44	4.339%	$58.8889	$58.89	$58.90	$58.90
7 purchase totals =	$700.62		$765.8762	$765.88	$765.90	$765.90