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	$140.56	11.827%	$157.184	$157.18	$157.20	$157.20
Purchase #2	$155.83	5.820%	$164.8993	$164.90	$164.90	$164.90
Purchase #3	$90.49	11.460%	$100.8602	$100.86	$100.85	$100.90
Purchase #4	$77.84	7.138%	$83.3962	$83.40	$83.40	$83.40
Purchase #5	$196.64	8.239%	$212.8412	$212.84	$212.85	$212.80
Purchase #6	$121.53	12.450%	$136.6605	$136.66	$136.65	$136.70
Purchase #7	$187.55	4.523%	$196.0329	$196.03	$196.05	$196.00
7 purchase totals =	$970.44		$1,051.8743	$1,051.87	$1,051.90	$1,051.90