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 $95.75   9.647%   $104.987   $104.99   $105.00   $105.00  
  Purchase #2 $208.27   9.320%   $227.6808   $227.68   $227.70   $227.70  
  Purchase #3 $102.71   13.389%   $116.4618   $116.46   $116.45   $116.50  
  Purchase #4 $8.25   9.467%   $9.031   $9.03   $9.05   $9.00  
  Purchase #5 $243.62   8.487%   $264.296   $264.30   $264.30   $264.30  
  Purchase #6 $215.94   4.266%   $225.152   $225.15   $225.15   $225.20  
  Purchase #7 $89.36   7.108%   $95.7117   $95.71   $95.70   $95.70  
  7 purchase totals = $963.90       $1,043.3203   $1,043.32   $1,043.35   $1,043.40