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 $58.68   3.489%   $60.7273   $60.73   $60.75   $60.70  
  Purchase #2 $201.84   10.851%   $223.7417   $223.74   $223.75   $223.70  
  Purchase #3 $187.86   10.124%   $206.8789   $206.88   $206.90   $206.90  
  Purchase #4 $201.98   13.597%   $229.4432   $229.44   $229.45   $229.40  
  Purchase #5 $68.83   7.688%   $74.1217   $74.12   $74.10   $74.10  
  Purchase #6 $234.98   10.610%   $259.9114   $259.91   $259.90   $259.90  
  Purchase #7 $54.50   4.410%   $56.9035   $56.90   $56.90   $56.90  
  7 purchase totals = $1,008.67       $1,111.7277   $1,111.72   $1,111.75   $1,111.60