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 $183.38   6.837%   $195.9177   $195.92   $195.90   $195.90  
  Purchase #2 $169.43   5.533%   $178.8046   $178.80   $178.80   $178.80  
  Purchase #3 $231.89   9.783%   $254.5758   $254.58   $254.60   $254.60  
  Purchase #4 $18.86   12.741%   $21.263   $21.26   $21.25   $21.30  
  Purchase #5 $247.76   4.209%   $258.1882   $258.19   $258.20   $258.20  
  Purchase #6 $93.74   8.787%   $101.9769   $101.98   $102.00   $102.00  
  Purchase #7 $106.64   8.601%   $115.8121   $115.81   $115.80   $115.80  
  7 purchase totals = $1,051.70       $1,126.5383   $1,126.54   $1,126.55   $1,126.60