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 $241.82   4.364%   $252.373   $252.37   $252.35   $252.40  
  Purchase #2 $199.59   9.200%   $217.9523   $217.95   $217.95   $218.00  
  Purchase #3 $143.96   7.257%   $154.4072   $154.41   $154.40   $154.40  
  Purchase #4 $130.61   7.125%   $139.916   $139.92   $139.90   $139.90  
  Purchase #5 $43.77   8.838%   $47.6384   $47.64   $47.65   $47.60  
  Purchase #6 $28.34   7.104%   $30.3533   $30.35   $30.35   $30.40  
  Purchase #7 $226.76   10.594%   $250.783   $250.78   $250.80   $250.80  
  7 purchase totals = $1,014.85       $1,093.4232   $1,093.42   $1,093.40   $1,093.50