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 $91.51   3.808%   $94.9947   $94.99   $95.00   $95.00  
  Purchase #2 $151.81   10.353%   $167.5269   $167.53   $167.55   $167.50  
  Purchase #3 $194.58   11.595%   $217.1416   $217.14   $217.15   $217.10  
  Purchase #4 $175.48   12.628%   $197.6396   $197.64   $197.65   $197.60  
  Purchase #5 $127.25   8.866%   $138.532   $138.53   $138.55   $138.50  
  Purchase #6 $179.76   9.429%   $196.7096   $196.71   $196.70   $196.70  
  Purchase #7 $6.49   11.299%   $7.2233   $7.22   $7.20   $7.20  
  7 purchase totals = $926.88       $1,019.7677   $1,019.76   $1,019.80   $1,019.60