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	$220.55	3.566%	$228.4148	$228.41	$228.40	$228.40
Purchase #2	$15.73	5.381%	$16.5764	$16.58	$16.60	$16.60
Purchase #3	$200.65	7.412%	$215.5222	$215.52	$215.50	$215.50
Purchase #4	$186.25	5.640%	$196.7545	$196.75	$196.75	$196.80
Purchase #5	$48.57	8.240%	$52.5722	$52.57	$52.55	$52.60
Purchase #6	$230.85	8.653%	$250.8255	$250.83	$250.85	$250.80
Purchase #7	$51.49	11.356%	$57.3372	$57.34	$57.35	$57.30
7 purchase totals =	$954.09		$1,018.0028	$1,018.00	$1,018.00	$1,018.00