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	$172.27	10.610%	$190.5478	$190.55	$190.55	$190.50
Purchase #2	$67.53	11.430%	$75.2487	$75.25	$75.25	$75.20
Purchase #3	$92.29	12.220%	$103.5678	$103.57	$103.55	$103.60
Purchase #4	$169.37	3.459%	$175.2285	$175.23	$175.25	$175.20
Purchase #5	$182.32	7.792%	$196.5264	$196.53	$196.55	$196.50
Purchase #6	$73.38	4.307%	$76.5405	$76.54	$76.55	$76.50
Purchase #7	$12.61	12.781%	$14.2217	$14.22	$14.20	$14.20
7 purchase totals =	$769.77		$831.8814	$831.89	$831.90	$831.70