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	$7.34	7.148%	$7.8647	$7.86	$7.85	$7.90
Purchase #2	$143.67	13.340%	$162.8356	$162.84	$162.85	$162.80
Purchase #3	$36.33	4.339%	$37.9064	$37.91	$37.90	$37.90
Purchase #4	$240.46	10.426%	$265.5304	$265.53	$265.55	$265.50
Purchase #5	$53.54	11.452%	$59.6714	$59.67	$59.65	$59.70
Purchase #6	$13.37	10.547%	$14.7801	$14.78	$14.80	$14.80
Purchase #7	$177.95	10.682%	$196.9586	$196.96	$196.95	$197.00
7 purchase totals =	$672.66		$745.5472	$745.55	$745.55	$745.60