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 $194.69   5.166%   $204.7477   $204.75   $204.75   $204.70  
  Purchase #2 $115.52   9.233%   $126.186   $126.19   $126.20   $126.20  
  Purchase #3 $145.83   7.841%   $157.2645   $157.26   $157.25   $157.30  
  Purchase #4 $170.46   11.802%   $190.5777   $190.58   $190.60   $190.60  
  Purchase #5 $213.90   10.824%   $237.0525   $237.05   $237.05   $237.10  
  Purchase #6 $60.96   7.638%   $65.6161   $65.62   $65.60   $65.60  
  Purchase #7 $12.83   7.392%   $13.7784   $13.78   $13.80   $13.80  
  7 purchase totals = $914.19       $995.2229   $995.23   $995.25   $995.30