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	$144.51	8.307%	$156.5144	$156.51	$156.50	$156.50
Purchase #2	$19.43	12.843%	$21.9254	$21.93	$21.95	$21.90
Purchase #3	$57.93	5.269%	$60.9823	$60.98	$61.00	$61.00
Purchase #4	$140.37	12.493%	$157.9064	$157.91	$157.90	$157.90
Purchase #5	$101.69	12.340%	$114.2385	$114.24	$114.25	$114.20
Purchase #6	$27.83	13.497%	$31.5862	$31.59	$31.60	$31.60
Purchase #7	$70.57	8.206%	$76.361	$76.36	$76.35	$76.40
7 purchase totals =	$562.33		$619.5142	$619.52	$619.55	$619.50