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 $116.72   7.300%   $125.2406   $125.24   $125.25   $125.20  
  Purchase #2 $135.62   3.107%   $139.8337   $139.83   $139.85   $139.80  
  Purchase #3 $220.41   6.415%   $234.5493   $234.55   $234.55   $234.50  
  Purchase #4 $118.56   6.755%   $126.5687   $126.57   $126.55   $126.60  
  Purchase #5 $143.92   3.466%   $148.9083   $148.91   $148.90   $148.90  
  Purchase #6 $9.93   9.265%   $10.85   $10.85   $10.85   $10.90  
  Purchase #7 $242.89   8.230%   $262.8798   $262.88   $262.90   $262.90  
  7 purchase totals = $988.05       $1,048.8304   $1,048.83   $1,048.85   $1,048.80