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	$164.73	6.558%	$175.533	$175.53	$175.55	$175.50
Purchase #2	$73.37	9.642%	$80.4443	$80.44	$80.45	$80.40
Purchase #3	$34.65	8.692%	$37.6618	$37.66	$37.65	$37.70
Purchase #4	$243.39	11.165%	$270.5645	$270.56	$270.55	$270.60
Purchase #5	$40.91	8.209%	$44.2683	$44.27	$44.25	$44.30
Purchase #6	$144.57	3.472%	$149.5895	$149.59	$149.60	$149.60
Purchase #7	$175.55	12.140%	$196.8618	$196.86	$196.85	$196.90
7 purchase totals =	$877.17		$954.9232	$954.91	$954.90	$955.00