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	$132.89	8.341%	$143.9744	$143.97	$143.95	$144.00
Purchase #2	$76.43	12.304%	$85.8339	$85.83	$85.85	$85.80
Purchase #3	$189.34	10.714%	$209.6259	$209.63	$209.65	$209.60
Purchase #4	$86.59	7.430%	$93.0236	$93.02	$93.00	$93.00
Purchase #5	$131.87	9.113%	$143.8873	$143.89	$143.90	$143.90
Purchase #6	$167.79	12.533%	$188.8191	$188.82	$188.80	$188.80
Purchase #7	$189.61	5.615%	$200.2566	$200.26	$200.25	$200.30
7 purchase totals =	$974.52		$1,065.4208	$1,065.42	$1,065.40	$1,065.40