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 $224.76   5.860%   $237.9309   $237.93   $237.95   $237.90  
  Purchase #2 $153.97   6.719%   $164.3152   $164.32   $164.30   $164.30  
  Purchase #3 $114.46   13.384%   $129.7793   $129.78   $129.80   $129.80  
  Purchase #4 $80.63   8.619%   $87.5795   $87.58   $87.60   $87.60  
  Purchase #5 $168.26   5.708%   $177.8643   $177.86   $177.85   $177.90  
  Purchase #6 $201.37   11.829%   $225.1901   $225.19   $225.20   $225.20  
  Purchase #7 $58.67   3.580%   $60.7704   $60.77   $60.75   $60.80  
  7 purchase totals = $1,002.12       $1,083.4297   $1,083.43   $1,083.45   $1,083.50