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	$52.58	8.692%	$57.1503	$57.15	$57.15	$57.20
Purchase #2	$238.47	7.307%	$255.895	$255.90	$255.90	$255.90
Purchase #3	$76.86	8.614%	$83.4807	$83.48	$83.50	$83.50
Purchase #4	$152.36	10.789%	$168.7981	$168.80	$168.80	$168.80
Purchase #5	$12.30	3.260%	$12.701	$12.70	$12.70	$12.70
Purchase #6	$70.44	8.564%	$76.4725	$76.47	$76.45	$76.50
Purchase #7	$170.26	10.348%	$187.8785	$187.88	$187.90	$187.90
7 purchase totals =	$773.27		$842.3761	$842.38	$842.40	$842.50