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 $210.95   10.466%   $233.028   $233.03   $233.05   $233.00  
  Purchase #2 $125.36   7.611%   $134.9011   $134.90   $134.90   $134.90  
  Purchase #3 $175.51   3.115%   $180.9771   $180.98   $181.00   $181.00  
  Purchase #4 $87.41   9.508%   $95.7209   $95.72   $95.70   $95.70  
  Purchase #5 $133.76   13.367%   $151.6397   $151.64   $151.65   $151.60  
  Purchase #6 $59.53   10.397%   $65.7193   $65.72   $65.70   $65.70  
  Purchase #7 $231.86   4.272%   $241.7651   $241.77   $241.75   $241.80  
  7 purchase totals = $1,024.38       $1,103.7512   $1,103.76   $1,103.75   $1,103.70