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	$177.82	10.520%	$196.5267	$196.53	$196.55	$196.50
Purchase #2	$43.64	12.863%	$49.2534	$49.25	$49.25	$49.30
Purchase #3	$59.34	10.233%	$65.4123	$65.41	$65.40	$65.40
Purchase #4	$245.43	7.525%	$263.8986	$263.90	$263.90	$263.90
Purchase #5	$36.92	10.583%	$40.8272	$40.83	$40.85	$40.80
Purchase #6	$52.71	6.648%	$56.2142	$56.21	$56.20	$56.20
Purchase #7	$94.43	6.185%	$100.2705	$100.27	$100.25	$100.30
7 purchase totals =	$710.29		$772.4029	$772.40	$772.40	$772.40