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	$132.93	13.166%	$150.4316	$150.43	$150.45	$150.40
Purchase #2	$182.33	7.812%	$196.5736	$196.57	$196.55	$196.60
Purchase #3	$238.35	11.639%	$266.0916	$266.09	$266.10	$266.10
Purchase #4	$118.35	11.134%	$131.5271	$131.53	$131.55	$131.50
Purchase #5	$103.69	3.130%	$106.9355	$106.94	$106.95	$106.90
Purchase #6	$64.63	6.614%	$68.9046	$68.90	$68.90	$68.90
Purchase #7	$238.66	9.330%	$260.927	$260.93	$260.95	$260.90
7 purchase totals =	$1,078.94		$1,181.3910	$1,181.39	$1,181.45	$1,181.30