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 $103.58   10.722%   $114.6858   $114.69   $114.70   $114.70  
  Purchase #2 $180.53   12.439%   $202.9861   $202.99   $203.00   $203.00  
  Purchase #3 $80.59   8.753%   $87.644   $87.64   $87.65   $87.60  
  Purchase #4 $217.59   3.756%   $225.7627   $225.76   $225.75   $225.80  
  Purchase #5 $200.37   7.207%   $214.8107   $214.81   $214.80   $214.80  
  Purchase #6 $177.62   12.661%   $200.1085   $200.11   $200.10   $200.10  
  Purchase #7 $22.79   12.727%   $25.6905   $25.69   $25.70   $25.70  
  7 purchase totals = $983.07       $1,071.6883   $1,071.69   $1,071.70   $1,071.70