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 $86.76   10.583%   $95.9418   $95.94   $95.95   $95.90  
  Purchase #2 $156.43   7.847%   $168.7051   $168.71   $168.70   $168.70  
  Purchase #3 $241.73   5.415%   $254.8197   $254.82   $254.80   $254.80  
  Purchase #4 $119.77   12.849%   $135.1592   $135.16   $135.15   $135.20  
  Purchase #5 $168.82   10.416%   $186.4043   $186.40   $186.40   $186.40  
  Purchase #6 $152.60   7.793%   $164.4921   $164.49   $164.50   $164.50  
  Purchase #7 $22.88   9.669%   $25.0923   $25.09   $25.10   $25.10  
  7 purchase totals = $948.99       $1,030.6145   $1,030.61   $1,030.60   $1,030.60