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 $56.78   9.678%   $62.2752   $62.28   $62.30   $62.30  
  Purchase #2 $219.88   10.793%   $243.6116   $243.61   $243.60   $243.60  
  Purchase #3 $82.48   5.650%   $87.1401   $87.14   $87.15   $87.10  
  Purchase #4 $236.80   5.617%   $250.1011   $250.10   $250.10   $250.10  
  Purchase #5 $227.94   5.164%   $239.7108   $239.71   $239.70   $239.70  
  Purchase #6 $9.56   8.551%   $10.3775   $10.38   $10.40   $10.40  
  Purchase #7 $107.76   7.360%   $115.6911   $115.69   $115.70   $115.70  
  7 purchase totals = $941.20       $1,008.9074   $1,008.91   $1,008.95   $1,008.90