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 $54.26   10.458%   $59.9345   $59.93   $59.95   $59.90  
  Purchase #2 $72.26   8.436%   $78.3559   $78.36   $78.35   $78.40  
  Purchase #3 $236.90   4.286%   $247.0535   $247.05   $247.05   $247.10  
  Purchase #4 $115.77   4.350%   $120.806   $120.81   $120.80   $120.80  
  Purchase #5 $204.73   6.455%   $217.9453   $217.95   $217.95   $217.90  
  Purchase #6 $248.27   3.226%   $256.2792   $256.28   $256.30   $256.30  
  Purchase #7 $225.73   11.452%   $251.5806   $251.58   $251.60   $251.60  
  7 purchase totals = $1,157.92       $1,231.9550   $1,231.96   $1,232.00   $1,232.00