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	$200.48	13.860%	$228.2665	$228.27	$228.25	$228.30
Purchase #2	$82.45	10.160%	$90.8269	$90.83	$90.85	$90.80
Purchase #3	$77.87	5.552%	$82.1933	$82.19	$82.20	$82.20
Purchase #4	$216.88	7.808%	$233.814	$233.81	$233.80	$233.80
Purchase #5	$84.78	3.359%	$87.6278	$87.63	$87.65	$87.60
Purchase #6	$223.31	10.513%	$246.7866	$246.79	$246.80	$246.80
Purchase #7	$76.83	13.190%	$86.9639	$86.96	$86.95	$87.00
7 purchase totals =	$962.60		$1,056.4790	$1,056.48	$1,056.50	$1,056.50