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 $214.46   8.701%   $233.1202   $233.12   $233.10   $233.10  
  Purchase #2 $35.78   3.188%   $36.9207   $36.92   $36.90   $36.90  
  Purchase #3 $177.36   6.481%   $188.8547   $188.85   $188.85   $188.90  
  Purchase #4 $182.71   12.360%   $205.293   $205.29   $205.30   $205.30  
  Purchase #5 $8.82   11.737%   $9.8552   $9.86   $9.85   $9.90  
  Purchase #6 $138.60   13.789%   $157.7116   $157.71   $157.70   $157.70  
  Purchase #7 $186.90   8.291%   $202.3959   $202.40   $202.40   $202.40  
  7 purchase totals = $944.63       $1,034.1513   $1,034.15   $1,034.10   $1,034.20