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 $119.81   5.122%   $125.9467   $125.95   $125.95   $125.90  
  Purchase #2 $29.90   6.104%   $31.7251   $31.73   $31.75   $31.70  
  Purchase #3 $185.70   8.260%   $201.0388   $201.04   $201.05   $201.00  
  Purchase #4 $163.43   11.442%   $182.1297   $182.13   $182.15   $182.10  
  Purchase #5 $131.28   5.400%   $138.3691   $138.37   $138.35   $138.40  
  Purchase #6 $61.40   4.467%   $64.1427   $64.14   $64.15   $64.10  
  Purchase #7 $59.47   5.811%   $62.9258   $62.93   $62.95   $62.90  
  7 purchase totals = $750.99       $806.2779   $806.29   $806.35   $806.10