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	$119.91	5.580%	$126.601	$126.60	$126.60	$126.60
Purchase #2	$132.79	8.631%	$144.2511	$144.25	$144.25	$144.30
Purchase #3	$78.33	12.205%	$87.8902	$87.89	$87.90	$87.90
Purchase #4	$112.41	4.132%	$117.0548	$117.05	$117.05	$117.10
Purchase #5	$33.32	12.486%	$37.4803	$37.48	$37.50	$37.50
Purchase #6	$196.30	9.641%	$215.2253	$215.23	$215.25	$215.20
Purchase #7	$248.46	13.300%	$281.5052	$281.51	$281.50	$281.50
7 purchase totals =	$921.52		$1,010.0079	$1,010.01	$1,010.05	$1,010.10