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 $92.57   3.424%   $95.7396   $95.74   $95.75   $95.70  
  Purchase #2 $153.35   4.796%   $160.7047   $160.70   $160.70   $160.70  
  Purchase #3 $95.68   6.693%   $102.0839   $102.08   $102.10   $102.10  
  Purchase #4 $166.71   5.525%   $175.9207   $175.92   $175.90   $175.90  
  Purchase #5 $57.81   4.439%   $60.3762   $60.38   $60.40   $60.40  
  Purchase #6 $56.32   10.298%   $62.1198   $62.12   $62.10   $62.10  
  Purchase #7 $143.71   6.325%   $152.7997   $152.80   $152.80   $152.80  
  7 purchase totals = $766.15       $809.7446   $809.74   $809.75   $809.70