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 $167.77   9.439%   $183.6058   $183.61   $183.60   $183.60  
  Purchase #2 $29.29   9.289%   $32.0107   $32.01   $32.00   $32.00  
  Purchase #3 $250.88   3.593%   $259.8941   $259.89   $259.90   $259.90  
  Purchase #4 $24.93   12.838%   $28.1305   $28.13   $28.15   $28.10  
  Purchase #5 $190.25   6.738%   $203.069   $203.07   $203.05   $203.10  
  Purchase #6 $208.42   13.314%   $236.169   $236.17   $236.15   $236.20  
  Purchase #7 $195.33   7.754%   $210.4759   $210.48   $210.50   $210.50  
  7 purchase totals = $1,066.87       $1,153.3550   $1,153.36   $1,153.35   $1,153.40