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 $67.45   10.746%   $74.6982   $74.70   $74.70   $74.70  
  Purchase #2 $210.78   3.740%   $218.6632   $218.66   $218.65   $218.70  
  Purchase #3 $169.25   9.477%   $185.2898   $185.29   $185.30   $185.30  
  Purchase #4 $145.75   13.688%   $165.7003   $165.70   $165.70   $165.70  
  Purchase #5 $236.90   6.650%   $252.6539   $252.65   $252.65   $252.70  
  Purchase #6 $17.38   10.221%   $19.1564   $19.16   $19.15   $19.20  
  Purchase #7 $87.31   8.447%   $94.6851   $94.69   $94.70   $94.70  
  7 purchase totals = $934.82       $1,010.8469   $1,010.85   $1,010.85   $1,011.00