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	$20.86	5.198%	$21.9443	$21.94	$21.95	$21.90
Purchase #2	$168.25	13.123%	$190.3294	$190.33	$190.35	$190.30
Purchase #3	$213.63	4.435%	$223.1045	$223.10	$223.10	$223.10
Purchase #4	$209.93	4.766%	$219.9353	$219.94	$219.95	$219.90
Purchase #5	$187.85	3.733%	$194.8624	$194.86	$194.85	$194.90
Purchase #6	$95.44	8.543%	$103.5934	$103.59	$103.60	$103.60
Purchase #7	$104.91	6.552%	$111.7837	$111.78	$111.80	$111.80
7 purchase totals =	$1,000.87		$1,065.5530	$1,065.54	$1,065.60	$1,065.50