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	$203.81	11.503%	$227.2543	$227.25	$227.25	$227.30
Purchase #2	$168.62	13.574%	$191.5085	$191.51	$191.50	$191.50
Purchase #3	$28.58	13.839%	$32.5352	$32.54	$32.55	$32.50
Purchase #4	$196.73	9.796%	$216.0017	$216.00	$216.00	$216.00
Purchase #5	$110.59	6.672%	$117.9686	$117.97	$117.95	$118.00
Purchase #6	$86.65	7.783%	$93.394	$93.39	$93.40	$93.40
Purchase #7	$36.30	12.534%	$40.8498	$40.85	$40.85	$40.80
7 purchase totals =	$831.28		$919.5121	$919.51	$919.50	$919.50