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 $128.66   10.134%   $141.6984   $141.70   $141.70   $141.70  
  Purchase #2 $103.70   10.566%   $114.6569   $114.66   $114.65   $114.70  
  Purchase #3 $220.34   7.201%   $236.2067   $236.21   $236.20   $236.20  
  Purchase #4 $218.90   10.436%   $241.7444   $241.74   $241.75   $241.70  
  Purchase #5 $102.87   11.373%   $114.5694   $114.57   $114.55   $114.60  
  Purchase #6 $53.73   8.754%   $58.4335   $58.43   $58.45   $58.40  
  Purchase #7 $38.76   12.663%   $43.6682   $43.67   $43.65   $43.70  
  7 purchase totals = $866.96       $950.9775   $950.98   $950.95   $951.00