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 $86.42   12.467%   $97.194   $97.19   $97.20   $97.20  
  Purchase #2 $134.27   4.813%   $140.7324   $140.73   $140.75   $140.70  
  Purchase #3 $244.80   11.856%   $273.8235   $273.82   $273.80   $273.80  
  Purchase #4 $166.69   12.180%   $186.9928   $186.99   $187.00   $187.00  
  Purchase #5 $60.94   3.775%   $63.2405   $63.24   $63.25   $63.20  
  Purchase #6 $224.94   6.195%   $238.875   $238.88   $238.90   $238.90  
  Purchase #7 $9.50   13.242%   $10.758   $10.76   $10.75   $10.80  
  7 purchase totals = $927.56       $1,011.6162   $1,011.61   $1,011.65   $1,011.60