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	$143.56	6.329%	$152.6459	$152.65	$152.65	$152.60
Purchase #2	$70.89	10.285%	$78.181	$78.18	$78.20	$78.20
Purchase #3	$85.68	5.306%	$90.2262	$90.23	$90.25	$90.20
Purchase #4	$127.29	10.359%	$140.476	$140.48	$140.50	$140.50
Purchase #5	$215.46	4.605%	$225.3819	$225.38	$225.40	$225.40
Purchase #6	$108.50	3.635%	$112.444	$112.44	$112.45	$112.40
Purchase #7	$236.29	11.318%	$263.0333	$263.03	$263.05	$263.00
7 purchase totals =	$987.67		$1,062.3883	$1,062.39	$1,062.50	$1,062.30