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 $73.55   12.326%   $82.6158   $82.62   $82.60   $82.60  
  Purchase #2 $237.27   9.444%   $259.6778   $259.68   $259.70   $259.70  
  Purchase #3 $67.29   3.442%   $69.6061   $69.61   $69.60   $69.60  
  Purchase #4 $226.88   6.524%   $241.6817   $241.68   $241.70   $241.70  
  Purchase #5 $30.48   4.253%   $31.7763   $31.78   $31.80   $31.80  
  Purchase #6 $118.50   6.119%   $125.751   $125.75   $125.75   $125.80  
  Purchase #7 $203.98   13.873%   $232.2781   $232.28   $232.30   $232.30  
  7 purchase totals = $957.95       $1,043.3868   $1,043.40   $1,043.45   $1,043.50