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 $119.71   5.502%   $126.2964   $126.30   $126.30   $126.30  
  Purchase #2 $74.77   3.391%   $77.3055   $77.31   $77.30   $77.30  
  Purchase #3 $58.31   7.654%   $62.773   $62.77   $62.75   $62.80  
  Purchase #4 $112.62   5.484%   $118.7961   $118.80   $118.80   $118.80  
  Purchase #5 $158.25   13.613%   $179.7926   $179.79   $179.80   $179.80  
  Purchase #6 $28.41   6.643%   $30.2973   $30.30   $30.30   $30.30  
  Purchase #7 $101.65   12.132%   $113.9822   $113.98   $114.00   $114.00  
  7 purchase totals = $653.72       $709.2431   $709.25   $709.25   $709.30