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	$159.59	3.158%	$164.6299	$164.63	$164.65	$164.60
Purchase #2	$212.72	12.138%	$238.54	$238.54	$238.55	$238.50
Purchase #3	$59.62	3.126%	$61.4837	$61.48	$61.50	$61.50
Purchase #4	$213.27	4.493%	$222.8522	$222.85	$222.85	$222.90
Purchase #5	$199.67	5.443%	$210.538	$210.54	$210.55	$210.50
Purchase #6	$103.87	12.502%	$116.8558	$116.86	$116.85	$116.90
Purchase #7	$68.67	10.761%	$76.0596	$76.06	$76.05	$76.10
7 purchase totals =	$1,017.41		$1,090.9592	$1,090.96	$1,091.00	$1,091.00