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 $182.82   10.728%   $202.4329   $202.43   $202.45   $202.40  
  Purchase #2 $166.56   6.726%   $177.7628   $177.76   $177.75   $177.80  
  Purchase #3 $198.85   9.596%   $217.9316   $217.93   $217.95   $217.90  
  Purchase #4 $108.29   12.371%   $121.6866   $121.69   $121.70   $121.70  
  Purchase #5 $90.92   3.847%   $94.4177   $94.42   $94.40   $94.40  
  Purchase #6 $92.83   4.667%   $97.1624   $97.16   $97.15   $97.20  
  Purchase #7 $39.51   5.179%   $41.5562   $41.56   $41.55   $41.60  
  7 purchase totals = $879.78       $952.9502   $952.95   $952.95   $953.00