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 $192.80   4.238%   $200.9709   $200.97   $200.95   $201.00  
  Purchase #2 $72.28   6.335%   $76.8589   $76.86   $76.85   $76.90  
  Purchase #3 $164.99   5.814%   $174.5825   $174.58   $174.60   $174.60  
  Purchase #4 $149.88   11.343%   $166.8809   $166.88   $166.90   $166.90  
  Purchase #5 $236.99   4.860%   $248.5077   $248.51   $248.50   $248.50  
  Purchase #6 $167.57   9.335%   $183.2127   $183.21   $183.20   $183.20  
  Purchase #7 $61.50   11.618%   $68.6451   $68.65   $68.65   $68.60  
  7 purchase totals = $1,046.01       $1,119.6587   $1,119.66   $1,119.65   $1,119.70