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 $126.88   3.448%   $131.2548   $131.25   $131.25   $131.30  
  Purchase #2 $114.49   10.814%   $126.8709   $126.87   $126.85   $126.90  
  Purchase #3 $64.61   9.250%   $70.5864   $70.59   $70.60   $70.60  
  Purchase #4 $127.31   11.290%   $141.6833   $141.68   $141.70   $141.70  
  Purchase #5 $203.53   3.851%   $211.3679   $211.37   $211.35   $211.40  
  Purchase #6 $187.81   8.847%   $204.4256   $204.43   $204.45   $204.40  
  Purchase #7 $56.59   12.656%   $63.752   $63.75   $63.75   $63.80  
  7 purchase totals = $881.22       $949.9409   $949.94   $949.95   $950.10