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 $61.94   12.515%   $69.6918   $69.69   $69.70   $69.70  
  Purchase #2 $129.57   13.627%   $147.2265   $147.23   $147.25   $147.20  
  Purchase #3 $94.50   8.419%   $102.456   $102.46   $102.45   $102.50  
  Purchase #4 $238.69   9.760%   $261.9861   $261.99   $262.00   $262.00  
  Purchase #5 $54.36   6.192%   $57.726   $57.73   $57.75   $57.70  
  Purchase #6 $170.81   8.757%   $185.7678   $185.77   $185.75   $185.80  
  Purchase #7 $187.85   6.372%   $199.8198   $199.82   $199.80   $199.80  
  7 purchase totals = $937.72       $1,024.6740   $1,024.69   $1,024.70   $1,024.70