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	$144.65	7.183%	$155.0402	$155.04	$155.05	$155.00
Purchase #2	$153.30	4.790%	$160.6431	$160.64	$160.65	$160.60
Purchase #3	$82.98	3.456%	$85.8478	$85.85	$85.85	$85.80
Purchase #4	$94.70	6.554%	$100.9066	$100.91	$100.90	$100.90
Purchase #5	$231.41	12.520%	$260.3825	$260.38	$260.40	$260.40
Purchase #6	$68.31	9.653%	$74.904	$74.90	$74.90	$74.90
Purchase #7	$230.39	12.121%	$258.3156	$258.32	$258.30	$258.30
7 purchase totals =	$1,005.74		$1,096.0398	$1,096.04	$1,096.05	$1,095.90