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	$164.50	11.485%	$183.3928	$183.39	$183.40	$183.40
Purchase #2	$76.47	13.235%	$86.5908	$86.59	$86.60	$86.60
Purchase #3	$141.88	10.421%	$156.6653	$156.67	$156.65	$156.70
Purchase #4	$215.70	10.618%	$238.603	$238.60	$238.60	$238.60
Purchase #5	$128.65	9.222%	$140.5141	$140.51	$140.50	$140.50
Purchase #6	$72.60	4.740%	$76.0412	$76.04	$76.05	$76.00
Purchase #7	$187.44	6.518%	$199.6573	$199.66	$199.65	$199.70
7 purchase totals =	$987.24		$1,081.4645	$1,081.46	$1,081.45	$1,081.50