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	$200.94	4.776%	$210.5369	$210.54	$210.55	$210.50
Purchase #2	$168.85	9.183%	$184.3555	$184.36	$184.35	$184.40
Purchase #3	$187.45	6.868%	$200.3241	$200.32	$200.30	$200.30
Purchase #4	$66.53	13.498%	$75.5102	$75.51	$75.50	$75.50
Purchase #5	$160.76	4.733%	$168.3688	$168.37	$168.35	$168.40
Purchase #6	$74.59	11.228%	$82.965	$82.97	$82.95	$83.00
Purchase #7	$199.33	4.599%	$208.4972	$208.50	$208.50	$208.50
7 purchase totals =	$1,058.45		$1,130.5577	$1,130.57	$1,130.50	$1,130.60