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	$59.90	5.245%	$63.0418	$63.04	$63.05	$63.00
Purchase #2	$56.66	7.380%	$60.8415	$60.84	$60.85	$60.80
Purchase #3	$182.83	9.743%	$200.6431	$200.64	$200.65	$200.60
Purchase #4	$197.30	7.762%	$212.6144	$212.61	$212.60	$212.60
Purchase #5	$157.45	12.326%	$176.8573	$176.86	$176.85	$176.90
Purchase #6	$98.90	12.573%	$111.3347	$111.33	$111.35	$111.30
Purchase #7	$36.34	3.241%	$37.5178	$37.52	$37.50	$37.50
7 purchase totals =	$789.38		$862.8506	$862.84	$862.85	$862.70