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 $81.46   13.623%   $92.5573   $92.56   $92.55   $92.60  
  Purchase #2 $101.25   12.319%   $113.723   $113.72   $113.70   $113.70  
  Purchase #3 $249.30   13.390%   $282.6813   $282.68   $282.70   $282.70  
  Purchase #4 $50.67   12.531%   $57.0195   $57.02   $57.00   $57.00  
  Purchase #5 $206.60   13.117%   $233.6997   $233.70   $233.70   $233.70  
  Purchase #6 $234.26   3.607%   $242.7098   $242.71   $242.70   $242.70  
  Purchase #7 $159.96   7.256%   $171.5667   $171.57   $171.55   $171.60  
  7 purchase totals = $1,083.50       $1,193.9573   $1,193.96   $1,193.90   $1,194.00