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	$140.58	11.116%	$156.2069	$156.21	$156.20	$156.20
Purchase #2	$208.94	11.661%	$233.3045	$233.30	$233.30	$233.30
Purchase #3	$28.50	12.326%	$32.0129	$32.01	$32.00	$32.00
Purchase #4	$38.61	8.275%	$41.805	$41.81	$41.80	$41.80
Purchase #5	$76.29	12.567%	$85.8774	$85.88	$85.90	$85.90
Purchase #6	$192.97	4.388%	$201.4375	$201.44	$201.45	$201.40
Purchase #7	$235.87	4.223%	$245.8308	$245.83	$245.85	$245.80
7 purchase totals =	$921.76		$996.4750	$996.48	$996.50	$996.40