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 $97.84   12.117%   $109.6953   $109.70   $109.70   $109.70  
  Purchase #2 $167.29   5.601%   $176.6599   $176.66   $176.65   $176.70  
  Purchase #3 $136.76   3.403%   $141.4139   $141.41   $141.40   $141.40  
  Purchase #4 $208.80   9.517%   $228.6715   $228.67   $228.65   $228.70  
  Purchase #5 $85.29   13.803%   $97.0626   $97.06   $97.05   $97.10  
  Purchase #6 $63.48   5.203%   $66.7829   $66.78   $66.80   $66.80  
  Purchase #7 $125.58   6.156%   $133.3107   $133.31   $133.30   $133.30  
  7 purchase totals = $885.04       $953.5968   $953.59   $953.55   $953.70