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	$62.45	4.356%	$65.1703	$65.17	$65.15	$65.20
Purchase #2	$135.42	12.800%	$152.7538	$152.75	$152.75	$152.80
Purchase #3	$176.59	6.334%	$187.7752	$187.78	$187.80	$187.80
Purchase #4	$139.67	3.496%	$144.5529	$144.55	$144.55	$144.60
Purchase #5	$129.50	6.868%	$138.3941	$138.39	$138.40	$138.40
Purchase #6	$234.83	13.250%	$265.945	$265.95	$265.95	$265.90
Purchase #7	$182.93	4.358%	$190.9021	$190.90	$190.90	$190.90
7 purchase totals =	$1,061.39		$1,145.4934	$1,145.49	$1,145.50	$1,145.60