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	$37.90	9.130%	$41.3603	$41.36	$41.35	$41.40
Purchase #2	$186.59	3.166%	$192.4974	$192.50	$192.50	$192.50
Purchase #3	$41.63	12.563%	$46.86	$46.86	$46.85	$46.90
Purchase #4	$204.48	10.364%	$225.6723	$225.67	$225.65	$225.70
Purchase #5	$133.44	9.784%	$146.4958	$146.50	$146.50	$146.50
Purchase #6	$112.54	4.655%	$117.7787	$117.78	$117.80	$117.80
Purchase #7	$180.54	8.688%	$196.2253	$196.23	$196.25	$196.20
7 purchase totals =	$897.12		$966.8898	$966.90	$966.90	$967.00