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 $51.36   12.838%   $57.9536   $57.95   $57.95   $58.00  
  Purchase #2 $86.54   12.259%   $97.1489   $97.15   $97.15   $97.10  
  Purchase #3 $239.69   11.682%   $267.6906   $267.69   $267.70   $267.70  
  Purchase #4 $199.49   6.677%   $212.8099   $212.81   $212.80   $212.80  
  Purchase #5 $230.67   5.794%   $244.035   $244.04   $244.05   $244.00  
  Purchase #6 $55.96   10.572%   $61.8761   $61.88   $61.90   $61.90  
  Purchase #7 $203.36   6.758%   $217.1031   $217.10   $217.10   $217.10  
  7 purchase totals = $1,067.07       $1,158.6172   $1,158.62   $1,158.65   $1,158.60