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 $61.78   4.676%   $64.6688   $64.67   $64.65   $64.70  
  Purchase #2 $91.87   4.220%   $95.7469   $95.75   $95.75   $95.70  
  Purchase #3 $23.36   4.334%   $24.3724   $24.37   $24.35   $24.40  
  Purchase #4 $82.96   12.271%   $93.14   $93.14   $93.15   $93.10  
  Purchase #5 $247.90   9.217%   $270.7489   $270.75   $270.75   $270.70  
  Purchase #6 $250.50   9.562%   $274.4528   $274.45   $274.45   $274.50  
  Purchase #7 $212.41   8.567%   $230.6072   $230.61   $230.60   $230.60  
  7 purchase totals = $970.78       $1,053.7370   $1,053.74   $1,053.70   $1,053.70