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 $84.51   11.148%   $93.9312   $93.93   $93.95   $93.90  
  Purchase #2 $205.38   13.720%   $233.5581   $233.56   $233.55   $233.60  
  Purchase #3 $223.85   13.689%   $254.4928   $254.49   $254.50   $254.50  
  Purchase #4 $235.45   6.455%   $250.6483   $250.65   $250.65   $250.60  
  Purchase #5 $56.94   13.421%   $64.5819   $64.58   $64.60   $64.60  
  Purchase #6 $131.94   3.798%   $136.9511   $136.95   $136.95   $137.00  
  Purchase #7 $78.46   7.427%   $84.2872   $84.29   $84.30   $84.30  
  7 purchase totals = $1,016.53       $1,118.4506   $1,118.45   $1,118.50   $1,118.50