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 $58.41   7.772%   $62.9496   $62.95   $62.95   $62.90  
  Purchase #2 $207.48   12.778%   $233.9918   $233.99   $234.00   $234.00  
  Purchase #3 $20.54   5.415%   $21.6522   $21.65   $21.65   $21.70  
  Purchase #4 $116.95   8.432%   $126.8112   $126.81   $126.80   $126.80  
  Purchase #5 $64.95   10.366%   $71.6827   $71.68   $71.70   $71.70  
  Purchase #6 $243.65   6.797%   $260.2109   $260.21   $260.20   $260.20  
  Purchase #7 $139.29   5.604%   $147.0958   $147.10   $147.10   $147.10  
  7 purchase totals = $851.27       $924.3942   $924.39   $924.40   $924.40