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 $73.95   11.170%   $82.2102   $82.21   $82.20   $82.20  
  Purchase #2 $97.57   8.538%   $105.9005   $105.90   $105.90   $105.90  
  Purchase #3 $104.49   10.697%   $115.6673   $115.67   $115.65   $115.70  
  Purchase #4 $193.28   6.441%   $205.7292   $205.73   $205.75   $205.70  
  Purchase #5 $128.66   11.184%   $143.0493   $143.05   $143.05   $143.00  
  Purchase #6 $59.93   11.776%   $66.9874   $66.99   $67.00   $67.00  
  Purchase #7 $32.85   12.816%   $37.0601   $37.06   $37.05   $37.10  
  7 purchase totals = $690.73       $756.6040   $756.61   $756.60   $756.60