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 $61.71   11.238%   $68.645   $68.65   $68.65   $68.60  
  Purchase #2 $134.26   6.633%   $143.1655   $143.17   $143.15   $143.20  
  Purchase #3 $185.96   11.272%   $206.9214   $206.92   $206.90   $206.90  
  Purchase #4 $182.64   4.469%   $190.8022   $190.80   $190.80   $190.80  
  Purchase #5 $176.35   8.286%   $190.9624   $190.96   $190.95   $191.00  
  Purchase #6 $196.28   11.371%   $218.599   $218.60   $218.60   $218.60  
  Purchase #7 $207.30   13.772%   $235.8494   $235.85   $235.85   $235.80  
  7 purchase totals = $1,144.50       $1,254.9449   $1,254.95   $1,254.90   $1,254.90