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 $86.49   10.456%   $95.5334   $95.53   $95.55   $95.50  
  Purchase #2 $245.63   12.374%   $276.0243   $276.02   $276.00   $276.00  
  Purchase #3 $179.36   9.343%   $196.1176   $196.12   $196.10   $196.10  
  Purchase #4 $21.94   7.336%   $23.5495   $23.55   $23.55   $23.50  
  Purchase #5 $15.31   7.717%   $16.4915   $16.49   $16.50   $16.50  
  Purchase #6 $231.66   6.249%   $246.1364   $246.14   $246.15   $246.10  
  Purchase #7 $243.76   5.335%   $256.7646   $256.76   $256.75   $256.80  
  7 purchase totals = $1,024.15       $1,110.6173   $1,110.61   $1,110.60   $1,110.50