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 $201.71   7.554%   $216.9472   $216.95   $216.95   $216.90  
  Purchase #2 $227.58   4.129%   $236.9768   $236.98   $237.00   $237.00  
  Purchase #3 $52.93   13.180%   $59.9062   $59.91   $59.90   $59.90  
  Purchase #4 $52.46   11.532%   $58.5097   $58.51   $58.50   $58.50  
  Purchase #5 $156.39   5.254%   $164.6067   $164.61   $164.60   $164.60  
  Purchase #6 $218.84   10.371%   $241.5359   $241.54   $241.55   $241.50  
  Purchase #7 $212.59   6.369%   $226.1299   $226.13   $226.15   $226.10  
  7 purchase totals = $1,122.50       $1,204.6124   $1,204.63   $1,204.65   $1,204.50