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 $43.68   7.455%   $46.9363   $46.94   $46.95   $46.90  
  Purchase #2 $55.69   9.458%   $60.9572   $60.96   $60.95   $61.00  
  Purchase #3 $227.81   6.516%   $242.6541   $242.65   $242.65   $242.70  
  Purchase #4 $104.40   5.160%   $109.787   $109.79   $109.80   $109.80  
  Purchase #5 $223.62   11.462%   $249.2513   $249.25   $249.25   $249.30  
  Purchase #6 $131.63   12.466%   $148.039   $148.04   $148.05   $148.00  
  Purchase #7 $118.30   4.867%   $124.0577   $124.06   $124.05   $124.10  
  7 purchase totals = $905.13       $981.6826   $981.69   $981.70   $981.80