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 $181.80   7.651%   $195.7095   $195.71   $195.70   $195.70  
  Purchase #2 $234.72   11.793%   $262.4005   $262.40   $262.40   $262.40  
  Purchase #3 $175.98   11.663%   $196.5045   $196.50   $196.50   $196.50  
  Purchase #4 $42.82   11.785%   $47.8663   $47.87   $47.85   $47.90  
  Purchase #5 $171.43   5.576%   $180.9889   $180.99   $181.00   $181.00  
  Purchase #6 $81.38   12.818%   $91.8113   $91.81   $91.80   $91.80  
  Purchase #7 $232.46   5.235%   $244.6293   $244.63   $244.65   $244.60  
  7 purchase totals = $1,120.59       $1,219.9103   $1,219.91   $1,219.90   $1,219.90