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 $63.54   9.447%   $69.5426   $69.54   $69.55   $69.50  
  Purchase #2 $241.58   4.245%   $251.8351   $251.84   $251.85   $251.80  
  Purchase #3 $34.82   8.318%   $37.7163   $37.72   $37.70   $37.70  
  Purchase #4 $205.53   13.721%   $233.7308   $233.73   $233.75   $233.70  
  Purchase #5 $113.97   8.630%   $123.8056   $123.81   $123.80   $123.80  
  Purchase #6 $41.71   11.132%   $46.3532   $46.35   $46.35   $46.40  
  Purchase #7 $242.51   3.357%   $250.6511   $250.65   $250.65   $250.70  
  7 purchase totals = $943.66       $1,013.6347   $1,013.64   $1,013.65   $1,013.60