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 $119.75   5.771%   $126.6608   $126.66   $126.65   $126.70  
  Purchase #2 $171.93   10.227%   $189.5133   $189.51   $189.50   $189.50  
  Purchase #3 $77.44   6.216%   $82.2537   $82.25   $82.25   $82.30  
  Purchase #4 $81.95   5.640%   $86.572   $86.57   $86.55   $86.60  
  Purchase #5 $232.47   7.697%   $250.3632   $250.36   $250.35   $250.40  
  Purchase #6 $55.31   12.562%   $62.258   $62.26   $62.25   $62.30  
  Purchase #7 $235.70   8.146%   $254.9001   $254.90   $254.90   $254.90  
  7 purchase totals = $974.55       $1,052.5211   $1,052.51   $1,052.45   $1,052.70