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	$186.89	9.614%	$204.8576	$204.86	$204.85	$204.90
Purchase #2	$207.41	5.353%	$218.5127	$218.51	$218.50	$218.50
Purchase #3	$208.37	11.617%	$232.5763	$232.58	$232.60	$232.60
Purchase #4	$112.96	9.587%	$123.7895	$123.79	$123.80	$123.80
Purchase #5	$243.79	12.790%	$274.9707	$274.97	$274.95	$275.00
Purchase #6	$84.32	7.806%	$90.902	$90.90	$90.90	$90.90
Purchase #7	$97.65	12.223%	$109.5858	$109.59	$109.60	$109.60
7 purchase totals =	$1,141.39		$1,255.1946	$1,255.20	$1,255.20	$1,255.30