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 $167.43   4.448%   $174.8773   $174.88   $174.90   $174.90  
  Purchase #2 $46.27   7.347%   $49.6695   $49.67   $49.65   $49.70  
  Purchase #3 $125.45   7.322%   $134.6354   $134.64   $134.65   $134.60  
  Purchase #4 $114.33   4.257%   $119.197   $119.20   $119.20   $119.20  
  Purchase #5 $221.34   5.717%   $233.994   $233.99   $234.00   $234.00  
  Purchase #6 $101.28   12.151%   $113.5865   $113.59   $113.60   $113.60  
  Purchase #7 $38.98   11.849%   $43.5987   $43.60   $43.60   $43.60  
  7 purchase totals = $815.08       $869.5584   $869.57   $869.60   $869.60