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	$147.97	12.234%	$166.0726	$166.07	$166.05	$166.10
Purchase #2	$207.96	3.676%	$215.6046	$215.60	$215.60	$215.60
Purchase #3	$95.86	6.176%	$101.7803	$101.78	$101.80	$101.80
Purchase #4	$162.70	10.431%	$179.6712	$179.67	$179.65	$179.70
Purchase #5	$107.57	10.497%	$118.8616	$118.86	$118.85	$118.90
Purchase #6	$100.56	10.682%	$111.3018	$111.30	$111.30	$111.30
Purchase #7	$199.96	11.309%	$222.5735	$222.57	$222.55	$222.60
7 purchase totals =	$1,022.58		$1,115.8656	$1,115.85	$1,115.80	$1,116.00