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	$222.89	7.329%	$239.2256	$239.23	$239.25	$239.20
Purchase #2	$207.47	5.745%	$219.3892	$219.39	$219.40	$219.40
Purchase #3	$50.59	11.679%	$56.4984	$56.50	$56.50	$56.50
Purchase #4	$73.79	12.273%	$82.8462	$82.85	$82.85	$82.80
Purchase #5	$205.46	10.311%	$226.645	$226.65	$226.65	$226.60
Purchase #6	$159.90	13.460%	$181.4225	$181.42	$181.40	$181.40
Purchase #7	$47.31	12.672%	$53.3051	$53.31	$53.30	$53.30
7 purchase totals =	$967.41		$1,059.3320	$1,059.35	$1,059.35	$1,059.20