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 $62.37   3.528%   $64.5704   $64.57   $64.55   $64.60  
  Purchase #2 $210.52   3.347%   $217.5661   $217.57   $217.55   $217.60  
  Purchase #3 $218.78   3.477%   $226.387   $226.39   $226.40   $226.40  
  Purchase #4 $231.94   12.821%   $261.677   $261.68   $261.70   $261.70  
  Purchase #5 $94.37   10.302%   $104.092   $104.09   $104.10   $104.10  
  Purchase #6 $182.74   13.762%   $207.8887   $207.89   $207.90   $207.90  
  Purchase #7 $13.69   3.183%   $14.1258   $14.13   $14.15   $14.10  
  7 purchase totals = $1,014.41       $1,096.3070   $1,096.32   $1,096.35   $1,096.40