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 $68.56   11.149%   $76.2038   $76.20   $76.20   $76.20  
  Purchase #2 $172.61   8.357%   $187.035   $187.04   $187.05   $187.00  
  Purchase #3 $216.99   4.369%   $226.4703   $226.47   $226.45   $226.50  
  Purchase #4 $18.65   5.365%   $19.6506   $19.65   $19.65   $19.70  
  Purchase #5 $233.34   10.192%   $257.122   $257.12   $257.10   $257.10  
  Purchase #6 $224.26   4.676%   $234.7464   $234.75   $234.75   $234.70  
  Purchase #7 $105.46   10.778%   $116.8265   $116.83   $116.85   $116.80  
  7 purchase totals = $1,039.87       $1,118.0546   $1,118.06   $1,118.05   $1,118.00