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 $84.75   9.563%   $92.8546   $92.85   $92.85   $92.90  
  Purchase #2 $149.29   5.427%   $157.392   $157.39   $157.40   $157.40  
  Purchase #3 $14.33   6.242%   $15.2245   $15.22   $15.20   $15.20  
  Purchase #4 $228.78   9.404%   $250.2945   $250.29   $250.30   $250.30  
  Purchase #5 $165.26   6.765%   $176.4398   $176.44   $176.45   $176.40  
  Purchase #6 $66.36   3.687%   $68.8067   $68.81   $68.80   $68.80  
  Purchase #7 $224.48   7.355%   $240.9905   $240.99   $241.00   $241.00  
  7 purchase totals = $933.25       $1,002.0026   $1,001.99   $1,002.00   $1,002.00