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 $161.33   8.456%   $174.9721   $174.97   $174.95   $175.00  
  Purchase #2 $187.89   8.244%   $203.3797   $203.38   $203.40   $203.40  
  Purchase #3 $250.25   10.216%   $275.8155   $275.82   $275.80   $275.80  
  Purchase #4 $157.64   8.382%   $170.8534   $170.85   $170.85   $170.90  
  Purchase #5 $32.56   8.504%   $35.3289   $35.33   $35.35   $35.30  
  Purchase #6 $53.92   6.326%   $57.331   $57.33   $57.35   $57.30  
  Purchase #7 $127.73   6.628%   $136.1959   $136.20   $136.20   $136.20  
  7 purchase totals = $971.32       $1,053.8765   $1,053.88   $1,053.90   $1,053.90