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 $61.34   10.110%   $67.5415   $67.54   $67.55   $67.50  
  Purchase #2 $212.32   9.461%   $232.4076   $232.41   $232.40   $232.40  
  Purchase #3 $156.41   8.572%   $169.8175   $169.82   $169.80   $169.80  
  Purchase #4 $157.51   13.520%   $178.8054   $178.81   $178.80   $178.80  
  Purchase #5 $163.33   12.291%   $183.4049   $183.40   $183.40   $183.40  
  Purchase #6 $77.43   5.563%   $81.7374   $81.74   $81.75   $81.70  
  Purchase #7 $113.46   6.160%   $120.4491   $120.45   $120.45   $120.40  
  7 purchase totals = $941.80       $1,034.1634   $1,034.17   $1,034.15   $1,034.00