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 $177.28   8.273%   $191.9464   $191.95   $191.95   $191.90  
  Purchase #2 $52.83   8.656%   $57.403   $57.40   $57.40   $57.40  
  Purchase #3 $36.70   6.404%   $39.0503   $39.05   $39.05   $39.10  
  Purchase #4 $6.33   6.585%   $6.7468   $6.75   $6.75   $6.70  
  Purchase #5 $121.33   10.603%   $134.1946   $134.19   $134.20   $134.20  
  Purchase #6 $126.68   8.791%   $137.8164   $137.82   $137.80   $137.80  
  Purchase #7 $176.52   8.144%   $190.8958   $190.90   $190.90   $190.90  
  7 purchase totals = $697.67       $758.0533   $758.06   $758.05   $758.00