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 $176.49   10.690%   $195.3568   $195.36   $195.35   $195.40  
  Purchase #2 $119.96   8.299%   $129.9155   $129.92   $129.90   $129.90  
  Purchase #3 $67.32   3.335%   $69.5651   $69.57   $69.55   $69.60  
  Purchase #4 $104.34   10.719%   $115.5242   $115.52   $115.50   $115.50  
  Purchase #5 $201.74   5.459%   $212.753   $212.75   $212.75   $212.80  
  Purchase #6 $166.88   13.744%   $189.816   $189.82   $189.80   $189.80  
  Purchase #7 $126.61   4.123%   $131.8301   $131.83   $131.85   $131.80  
  7 purchase totals = $963.34       $1,044.7607   $1,044.77   $1,044.70   $1,044.80