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 $202.66   7.108%   $217.0651   $217.07   $217.05   $217.10  
  Purchase #2 $33.62   4.582%   $35.1605   $35.16   $35.15   $35.20  
  Purchase #3 $94.40   11.846%   $105.5826   $105.58   $105.60   $105.60  
  Purchase #4 $161.61   9.544%   $177.0341   $177.03   $177.05   $177.00  
  Purchase #5 $245.91   3.177%   $253.7226   $253.72   $253.70   $253.70  
  Purchase #6 $53.43   5.208%   $56.2126   $56.21   $56.20   $56.20  
  Purchase #7 $221.48   4.739%   $231.9759   $231.98   $232.00   $232.00  
  7 purchase totals = $1,013.11       $1,076.7534   $1,076.75   $1,076.75   $1,076.80