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	$32.34	12.796%	$36.4782	$36.48	$36.50	$36.50
Purchase #2	$86.39	4.823%	$90.5566	$90.56	$90.55	$90.60
Purchase #3	$153.78	8.762%	$167.2542	$167.25	$167.25	$167.30
Purchase #4	$212.99	8.798%	$231.7289	$231.73	$231.75	$231.70
Purchase #5	$172.89	13.729%	$196.6261	$196.63	$196.65	$196.60
Purchase #6	$201.38	12.765%	$227.0862	$227.09	$227.10	$227.10
Purchase #7	$180.66	6.245%	$191.9422	$191.94	$191.95	$191.90
7 purchase totals =	$1,040.43		$1,141.6724	$1,141.68	$1,141.75	$1,141.70