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 $86.32   10.126%   $95.0608   $95.06   $95.05   $95.10  
  Purchase #2 $157.57   8.275%   $170.6089   $170.61   $170.60   $170.60  
  Purchase #3 $50.94   5.655%   $53.8207   $53.82   $53.80   $53.80  
  Purchase #4 $140.87   11.813%   $157.511   $157.51   $157.50   $157.50  
  Purchase #5 $65.37   12.609%   $73.6125   $73.61   $73.60   $73.60  
  Purchase #6 $160.63   13.247%   $181.9087   $181.91   $181.90   $181.90  
  Purchase #7 $57.30   5.618%   $60.5191   $60.52   $60.50   $60.50  
  7 purchase totals = $719.00       $793.0417   $793.04   $792.95   $793.00