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 $56.81   9.243%   $62.0609   $62.06   $62.05   $62.10  
  Purchase #2 $206.40   9.616%   $226.2474   $226.25   $226.25   $226.20  
  Purchase #3 $155.67   10.253%   $171.6308   $171.63   $171.65   $171.60  
  Purchase #4 $235.77   13.707%   $268.087   $268.09   $268.10   $268.10  
  Purchase #5 $47.78   10.651%   $52.869   $52.87   $52.85   $52.90  
  Purchase #6 $227.66   13.484%   $258.3577   $258.36   $258.35   $258.40  
  Purchase #7 $80.88   9.452%   $88.5248   $88.52   $88.50   $88.50  
  7 purchase totals = $1,010.97       $1,127.7776   $1,127.78   $1,127.75   $1,127.80