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 $228.62   6.551%   $243.5969   $243.60   $243.60   $243.60  
  Purchase #2 $248.51   5.527%   $262.2451   $262.25   $262.25   $262.20  
  Purchase #3 $229.60   10.655%   $254.0639   $254.06   $254.05   $254.10  
  Purchase #4 $90.82   11.360%   $101.1372   $101.14   $101.15   $101.10  
  Purchase #5 $53.72   13.520%   $60.9829   $60.98   $61.00   $61.00  
  Purchase #6 $126.36   9.850%   $138.8065   $138.81   $138.80   $138.80  
  Purchase #7 $200.47   5.129%   $210.7521   $210.75   $210.75   $210.80  
  7 purchase totals = $1,178.10       $1,271.5846   $1,271.59   $1,271.60   $1,271.60