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 $83.97   13.840%   $95.5914   $95.59   $95.60   $95.60  
  Purchase #2 $5.26   9.300%   $5.7492   $5.75   $5.75   $5.70  
  Purchase #3 $32.33   11.357%   $36.0017   $36.00   $36.00   $36.00  
  Purchase #4 $152.85   6.460%   $162.7241   $162.72   $162.70   $162.70  
  Purchase #5 $245.54   4.161%   $255.7569   $255.76   $255.75   $255.80  
  Purchase #6 $245.44   12.698%   $276.606   $276.61   $276.60   $276.60  
  Purchase #7 $214.84   7.610%   $231.1893   $231.19   $231.20   $231.20  
  7 purchase totals = $980.23       $1,063.6186   $1,063.62   $1,063.60   $1,063.60