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	$104.70	13.290%	$118.6146	$118.61	$118.60	$118.60
Purchase #2	$233.53	6.405%	$248.4876	$248.49	$248.50	$248.50
Purchase #3	$66.40	8.548%	$72.0759	$72.08	$72.10	$72.10
Purchase #4	$10.33	5.365%	$10.8842	$10.88	$10.90	$10.90
Purchase #5	$172.98	13.838%	$196.917	$196.92	$196.90	$196.90
Purchase #6	$205.31	8.307%	$222.3651	$222.37	$222.35	$222.40
Purchase #7	$140.75	13.254%	$159.405	$159.41	$159.40	$159.40
7 purchase totals =	$934.00		$1,028.7494	$1,028.76	$1,028.75	$1,028.80