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	$144.50	4.240%	$150.6268	$150.63	$150.65	$150.60
Purchase #2	$216.56	7.738%	$233.3174	$233.32	$233.30	$233.30
Purchase #3	$71.50	13.810%	$81.3742	$81.37	$81.35	$81.40
Purchase #4	$136.59	13.233%	$154.665	$154.67	$154.65	$154.70
Purchase #5	$76.99	13.402%	$87.3082	$87.31	$87.30	$87.30
Purchase #6	$67.32	13.781%	$76.5974	$76.60	$76.60	$76.60
Purchase #7	$111.60	5.426%	$117.6554	$117.66	$117.65	$117.70
7 purchase totals =	$825.06		$901.5444	$901.56	$901.50	$901.60