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 $151.92   8.815%   $165.3117   $165.31   $165.30   $165.30  
  Purchase #2 $178.31   9.810%   $195.8022   $195.80   $195.80   $195.80  
  Purchase #3 $97.44   11.600%   $108.743   $108.74   $108.75   $108.70  
  Purchase #4 $228.76   10.180%   $252.0478   $252.05   $252.05   $252.00  
  Purchase #5 $59.61   5.641%   $62.9726   $62.97   $62.95   $63.00  
  Purchase #6 $12.77   5.558%   $13.4798   $13.48   $13.50   $13.50  
  Purchase #7 $240.47   9.125%   $262.4129   $262.41   $262.40   $262.40  
  7 purchase totals = $969.28       $1,060.7700   $1,060.76   $1,060.75   $1,060.70