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 $58.66   5.738%   $62.0259   $62.03   $62.05   $62.00  
  Purchase #2 $156.88   5.607%   $165.6763   $165.68   $165.70   $165.70  
  Purchase #3 $27.78   4.173%   $28.9393   $28.94   $28.95   $28.90  
  Purchase #4 $224.99   11.190%   $250.1664   $250.17   $250.15   $250.20  
  Purchase #5 $233.63   7.205%   $250.463   $250.46   $250.45   $250.50  
  Purchase #6 $105.79   3.537%   $109.5318   $109.53   $109.55   $109.50  
  Purchase #7 $158.47   11.802%   $177.1726   $177.17   $177.15   $177.20  
  7 purchase totals = $966.20       $1,043.9753   $1,043.98   $1,044.00   $1,044.00