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 $210.56   12.844%   $237.6043   $237.60   $237.60   $237.60  
  Purchase #2 $34.73   6.396%   $36.9513   $36.95   $36.95   $37.00  
  Purchase #3 $241.59   5.512%   $254.9064   $254.91   $254.90   $254.90  
  Purchase #4 $156.30   4.723%   $163.682   $163.68   $163.70   $163.70  
  Purchase #5 $102.47   4.695%   $107.281   $107.28   $107.30   $107.30  
  Purchase #6 $236.56   9.603%   $259.2769   $259.28   $259.30   $259.30  
  Purchase #7 $186.47   9.219%   $203.6607   $203.66   $203.65   $203.70  
  7 purchase totals = $1,168.68       $1,263.3626   $1,263.36   $1,263.40   $1,263.50