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	$240.70	7.780%	$259.4265	$259.43	$259.45	$259.40
Purchase #2	$202.43	13.336%	$229.4261	$229.43	$229.45	$229.40
Purchase #3	$92.94	9.307%	$101.5899	$101.59	$101.60	$101.60
Purchase #4	$73.51	6.532%	$78.3117	$78.31	$78.30	$78.30
Purchase #5	$65.60	4.460%	$68.5258	$68.53	$68.55	$68.50
Purchase #6	$129.44	11.709%	$144.5961	$144.60	$144.60	$144.60
Purchase #7	$242.61	6.761%	$259.0129	$259.01	$259.00	$259.00
7 purchase totals =	$1,047.23		$1,140.8890	$1,140.90	$1,140.95	$1,140.80