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	$230.69	6.388%	$245.4265	$245.43	$245.45	$245.40
Purchase #2	$38.59	7.165%	$41.355	$41.36	$41.35	$41.40
Purchase #3	$165.94	5.809%	$175.5795	$175.58	$175.60	$175.60
Purchase #4	$119.56	11.746%	$133.6035	$133.60	$133.60	$133.60
Purchase #5	$217.39	12.630%	$244.8464	$244.85	$244.85	$244.80
Purchase #6	$198.46	10.149%	$218.6017	$218.60	$218.60	$218.60
Purchase #7	$168.72	13.159%	$190.9219	$190.92	$190.90	$190.90
7 purchase totals =	$1,139.35		$1,250.3345	$1,250.34	$1,250.35	$1,250.30