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	$141.28	13.827%	$160.8148	$160.81	$160.80	$160.80
Purchase #2	$187.39	7.719%	$201.8546	$201.85	$201.85	$201.90
Purchase #3	$78.85	8.165%	$85.2881	$85.29	$85.30	$85.30
Purchase #4	$195.43	11.835%	$218.5591	$218.56	$218.55	$218.60
Purchase #5	$175.92	5.718%	$185.9791	$185.98	$186.00	$186.00
Purchase #6	$139.40	10.109%	$153.4919	$153.49	$153.50	$153.50
Purchase #7	$29.99	9.661%	$32.8873	$32.89	$32.90	$32.90
7 purchase totals =	$948.26		$1,038.8749	$1,038.87	$1,038.90	$1,039.00