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 $215.33   8.528%   $233.6933   $233.69   $233.70   $233.70  
  Purchase #2 $219.39   8.353%   $237.7156   $237.72   $237.70   $237.70  
  Purchase #3 $151.45   6.381%   $161.114   $161.11   $161.10   $161.10  
  Purchase #4 $231.94   8.281%   $251.147   $251.15   $251.15   $251.10  
  Purchase #5 $18.76   7.726%   $20.2094   $20.21   $20.20   $20.20  
  Purchase #6 $226.31   9.756%   $248.3888   $248.39   $248.40   $248.40  
  Purchase #7 $207.44   8.461%   $224.9915   $224.99   $225.00   $225.00  
  7 purchase totals = $1,270.62       $1,377.2596   $1,377.26   $1,377.25   $1,377.20