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 $33.66   5.814%   $35.617   $35.62   $35.60   $35.60  
  Purchase #2 $212.31   12.330%   $238.4878   $238.49   $238.50   $238.50  
  Purchase #3 $101.91   6.479%   $108.5127   $108.51   $108.50   $108.50  
  Purchase #4 $212.30   8.475%   $230.2924   $230.29   $230.30   $230.30  
  Purchase #5 $24.57   4.606%   $25.7017   $25.70   $25.70   $25.70  
  Purchase #6 $227.33   4.652%   $237.9054   $237.91   $237.90   $237.90  
  Purchase #7 $113.51   12.844%   $128.0892   $128.09   $128.10   $128.10  
  7 purchase totals = $925.59       $1,004.6062   $1,004.61   $1,004.60   $1,004.60