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	$81.85	5.171%	$86.0825	$86.08	$86.10	$86.10
Purchase #2	$148.88	11.527%	$166.0414	$166.04	$166.05	$166.00
Purchase #3	$80.46	8.174%	$87.0368	$87.04	$87.05	$87.00
Purchase #4	$206.91	6.230%	$219.8005	$219.80	$219.80	$219.80
Purchase #5	$210.47	3.519%	$217.8764	$217.88	$217.90	$217.90
Purchase #6	$179.39	11.520%	$200.0557	$200.06	$200.05	$200.10
Purchase #7	$210.56	4.424%	$219.8752	$219.88	$219.90	$219.90
7 purchase totals =	$1,118.52		$1,196.7685	$1,196.78	$1,196.85	$1,196.80