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 $176.48   9.520%   $193.2809   $193.28   $193.30   $193.30  
  Purchase #2 $210.92   11.183%   $234.5072   $234.51   $234.50   $234.50  
  Purchase #3 $63.53   4.440%   $66.3507   $66.35   $66.35   $66.40  
  Purchase #4 $123.94   13.319%   $140.4476   $140.45   $140.45   $140.40  
  Purchase #5 $247.67   7.215%   $265.5394   $265.54   $265.55   $265.50  
  Purchase #6 $239.47   8.324%   $259.4035   $259.40   $259.40   $259.40  
  Purchase #7 $13.81   6.751%   $14.7423   $14.74   $14.75   $14.70  
  7 purchase totals = $1,075.82       $1,174.2716   $1,174.27   $1,174.30   $1,174.20