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	$216.78	8.679%	$235.5943	$235.59	$235.60	$235.60
Purchase #2	$196.96	13.549%	$223.6461	$223.65	$223.65	$223.60
Purchase #3	$241.56	12.747%	$272.3517	$272.35	$272.35	$272.40
Purchase #4	$104.43	7.837%	$112.6142	$112.61	$112.60	$112.60
Purchase #5	$52.59	8.846%	$57.2421	$57.24	$57.25	$57.20
Purchase #6	$103.83	7.230%	$111.3369	$111.34	$111.35	$111.30
Purchase #7	$117.72	3.156%	$121.4352	$121.44	$121.45	$121.40
7 purchase totals =	$1,033.87		$1,134.2205	$1,134.22	$1,134.25	$1,134.10