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 $241.46   8.517%   $262.0251   $262.03   $262.05   $262.00  
  Purchase #2 $125.26   4.682%   $131.1247   $131.12   $131.10   $131.10  
  Purchase #3 $130.31   9.798%   $143.0778   $143.08   $143.10   $143.10  
  Purchase #4 $225.50   8.855%   $245.468   $245.47   $245.45   $245.50  
  Purchase #5 $216.43   9.873%   $237.7981   $237.80   $237.80   $237.80  
  Purchase #6 $137.35   4.460%   $143.4758   $143.48   $143.50   $143.50  
  Purchase #7 $78.84   13.744%   $89.6758   $89.68   $89.70   $89.70  
  7 purchase totals = $1,155.15       $1,252.6453   $1,252.66   $1,252.70   $1,252.70