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 $219.74   10.528%   $242.8742   $242.87   $242.85   $242.90  
  Purchase #2 $89.40   6.660%   $95.354   $95.35   $95.35   $95.40  
  Purchase #3 $207.82   6.212%   $220.7298   $220.73   $220.75   $220.70  
  Purchase #4 $10.48   7.786%   $11.296   $11.30   $11.30   $11.30  
  Purchase #5 $246.92   11.368%   $274.9899   $274.99   $275.00   $275.00  
  Purchase #6 $246.68   8.857%   $268.5284   $268.53   $268.55   $268.50  
  Purchase #7 $5.39   6.805%   $5.7568   $5.76   $5.75   $5.80  
  7 purchase totals = $1,026.43       $1,119.5291   $1,119.53   $1,119.55   $1,119.60