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 $232.81   12.828%   $262.6749   $262.67   $262.65   $262.70  
  Purchase #2 $127.48   10.754%   $141.1892   $141.19   $141.20   $141.20  
  Purchase #3 $101.86   9.721%   $111.7618   $111.76   $111.75   $111.80  
  Purchase #4 $79.76   9.597%   $87.4146   $87.41   $87.40   $87.40  
  Purchase #5 $221.42   3.281%   $228.6848   $228.68   $228.70   $228.70  
  Purchase #6 $123.98   12.357%   $139.3002   $139.30   $139.30   $139.30  
  Purchase #7 $226.89   3.429%   $234.6701   $234.67   $234.65   $234.70  
  7 purchase totals = $1,114.20       $1,205.6956   $1,205.68   $1,205.65   $1,205.80