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 $176.92   13.725%   $201.2023   $201.20   $201.20   $201.20  
  Purchase #2 $174.60   12.544%   $196.5018   $196.50   $196.50   $196.50  
  Purchase #3 $198.76   4.349%   $207.4041   $207.40   $207.40   $207.40  
  Purchase #4 $209.94   7.813%   $226.3426   $226.34   $226.35   $226.30  
  Purchase #5 $22.44   3.676%   $23.2649   $23.26   $23.25   $23.30  
  Purchase #6 $118.87   12.392%   $133.6004   $133.60   $133.60   $133.60  
  Purchase #7 $175.46   6.760%   $187.3211   $187.32   $187.30   $187.30  
  7 purchase totals = $1,076.99       $1,175.6372   $1,175.62   $1,175.60   $1,175.60