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	$107.57	8.646%	$116.8705	$116.87	$116.85	$116.90
Purchase #2	$244.49	6.515%	$260.4185	$260.42	$260.40	$260.40
Purchase #3	$93.50	6.266%	$99.3587	$99.36	$99.35	$99.40
Purchase #4	$150.73	11.783%	$168.4905	$168.49	$168.50	$168.50
Purchase #5	$138.79	9.827%	$152.4289	$152.43	$152.45	$152.40
Purchase #6	$107.36	10.758%	$118.9098	$118.91	$118.90	$118.90
Purchase #7	$217.39	7.618%	$233.9508	$233.95	$233.95	$234.00
7 purchase totals =	$1,059.83		$1,150.4277	$1,150.43	$1,150.40	$1,150.50