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 $208.74   12.660%   $235.1665   $235.17   $235.15   $235.20  
  Purchase #2 $212.29   8.645%   $230.6425   $230.64   $230.65   $230.60  
  Purchase #3 $220.50   8.353%   $238.9184   $238.92   $238.90   $238.90  
  Purchase #4 $55.99   9.688%   $61.4143   $61.41   $61.40   $61.40  
  Purchase #5 $60.76   8.413%   $65.8717   $65.87   $65.85   $65.90  
  Purchase #6 $19.45   8.428%   $21.0892   $21.09   $21.10   $21.10  
  Purchase #7 $89.85   5.686%   $94.9589   $94.96   $94.95   $95.00  
  7 purchase totals = $867.58       $948.0615   $948.06   $948.00   $948.10