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 $57.95   5.730%   $61.2705   $61.27   $61.25   $61.30  
  Purchase #2 $191.72   7.380%   $205.8689   $205.87   $205.85   $205.90  
  Purchase #3 $191.51   5.143%   $201.3594   $201.36   $201.35   $201.40  
  Purchase #4 $203.81   6.447%   $216.9496   $216.95   $216.95   $216.90  
  Purchase #5 $219.85   5.242%   $231.3745   $231.37   $231.35   $231.40  
  Purchase #6 $201.69   5.414%   $212.6095   $212.61   $212.60   $212.60  
  Purchase #7 $244.85   3.817%   $254.1959   $254.20   $254.20   $254.20  
  7 purchase totals = $1,311.38       $1,383.6283   $1,383.63   $1,383.55   $1,383.70