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	$141.89	4.149%	$147.777	$147.78	$147.80	$147.80
Purchase #2	$147.78	12.450%	$166.1786	$166.18	$166.20	$166.20
Purchase #3	$244.44	8.775%	$265.8896	$265.89	$265.90	$265.90
Purchase #4	$171.46	3.181%	$176.9141	$176.91	$176.90	$176.90
Purchase #5	$19.34	7.619%	$20.8135	$20.81	$20.80	$20.80
Purchase #6	$11.57	4.431%	$12.0827	$12.08	$12.10	$12.10
Purchase #7	$224.80	13.646%	$255.4762	$255.48	$255.50	$255.50
7 purchase totals =	$961.28		$1,045.1317	$1,045.13	$1,045.20	$1,045.20