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 $34.48   6.524%   $36.7295   $36.73   $36.75   $36.70  
  Purchase #2 $198.28   7.706%   $213.5595   $213.56   $213.55   $213.60  
  Purchase #3 $113.53   10.451%   $125.395   $125.40   $125.40   $125.40  
  Purchase #4 $201.69   9.549%   $220.9494   $220.95   $220.95   $220.90  
  Purchase #5 $155.56   8.132%   $168.2101   $168.21   $168.20   $168.20  
  Purchase #6 $150.77   8.435%   $163.4874   $163.49   $163.50   $163.50  
  Purchase #7 $119.48   4.114%   $124.3954   $124.40   $124.40   $124.40  
  7 purchase totals = $973.79       $1,052.7263   $1,052.74   $1,052.75   $1,052.70