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 $34.28   6.328%   $36.4492   $36.45   $36.45   $36.40  
  Purchase #2 $197.80   9.135%   $215.869   $215.87   $215.85   $215.90  
  Purchase #3 $66.52   11.167%   $73.9483   $73.95   $73.95   $73.90  
  Purchase #4 $210.63   13.438%   $238.9345   $238.93   $238.95   $238.90  
  Purchase #5 $225.70   8.599%   $245.1079   $245.11   $245.10   $245.10  
  Purchase #6 $192.92   7.526%   $207.4392   $207.44   $207.45   $207.40  
  Purchase #7 $44.98   11.543%   $50.172   $50.17   $50.15   $50.20  
  7 purchase totals = $972.83       $1,067.9201   $1,067.92   $1,067.90   $1,067.80