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 $76.96   12.399%   $86.5023   $86.50   $86.50   $86.50  
  Purchase #2 $91.37   4.241%   $95.245   $95.25   $95.25   $95.20  
  Purchase #3 $220.52   8.613%   $239.5134   $239.51   $239.50   $239.50  
  Purchase #4 $226.33   8.452%   $245.4594   $245.46   $245.45   $245.50  
  Purchase #5 $226.49   11.577%   $252.7107   $252.71   $252.70   $252.70  
  Purchase #6 $76.63   5.803%   $81.0768   $81.08   $81.10   $81.10  
  Purchase #7 $41.31   7.811%   $44.5367   $44.54   $44.55   $44.50  
  7 purchase totals = $959.61       $1,045.0443   $1,045.05   $1,045.05   $1,045.00