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	$79.63	3.435%	$82.3653	$82.37	$82.35	$82.40
Purchase #2	$231.98	10.749%	$256.9155	$256.92	$256.90	$256.90
Purchase #3	$107.64	5.554%	$113.6183	$113.62	$113.60	$113.60
Purchase #4	$41.90	3.361%	$43.3083	$43.31	$43.30	$43.30
Purchase #5	$198.58	11.215%	$220.8507	$220.85	$220.85	$220.90
Purchase #6	$232.67	8.137%	$251.6024	$251.60	$251.60	$251.60
Purchase #7	$110.47	5.697%	$116.7635	$116.76	$116.75	$116.80
7 purchase totals =	$1,002.87		$1,085.4240	$1,085.43	$1,085.35	$1,085.50