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 $93.41   13.780%   $106.2819   $106.28   $106.30   $106.30  
  Purchase #2 $115.69   8.738%   $125.799   $125.80   $125.80   $125.80  
  Purchase #3 $58.56   12.185%   $65.6955   $65.70   $65.70   $65.70  
  Purchase #4 $110.40   13.834%   $125.6727   $125.67   $125.65   $125.70  
  Purchase #5 $93.36   6.736%   $99.6487   $99.65   $99.65   $99.60  
  Purchase #6 $180.72   11.747%   $201.9492   $201.95   $201.95   $201.90  
  Purchase #7 $241.55   8.511%   $262.1083   $262.11   $262.10   $262.10  
  7 purchase totals = $893.69       $987.1553   $987.16   $987.15   $987.10