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 $60.89   4.716%   $63.7616   $63.76   $63.75   $63.80  
  Purchase #2 $231.60   11.287%   $257.7407   $257.74   $257.75   $257.70  
  Purchase #3 $34.74   10.154%   $38.2675   $38.27   $38.25   $38.30  
  Purchase #4 $242.83   5.502%   $256.1905   $256.19   $256.20   $256.20  
  Purchase #5 $157.40   5.276%   $165.7044   $165.70   $165.70   $165.70  
  Purchase #6 $168.98   6.343%   $179.6984   $179.70   $179.70   $179.70  
  Purchase #7 $216.50   13.350%   $245.4028   $245.40   $245.40   $245.40  
  7 purchase totals = $1,112.94       $1,206.7659   $1,206.76   $1,206.75   $1,206.80