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 $194.46   3.469%   $201.2058   $201.21   $201.20   $201.20  
  Purchase #2 $62.88   4.322%   $65.5977   $65.60   $65.60   $65.60  
  Purchase #3 $22.53   4.287%   $23.4959   $23.50   $23.50   $23.50  
  Purchase #4 $71.26   11.134%   $79.1941   $79.19   $79.20   $79.20  
  Purchase #5 $55.55   5.493%   $58.6014   $58.60   $58.60   $58.60  
  Purchase #6 $66.27   8.460%   $71.8764   $71.88   $71.90   $71.90  
  Purchase #7 $138.88   12.113%   $155.7025   $155.70   $155.70   $155.70  
  7 purchase totals = $611.83       $655.6738   $655.68   $655.70   $655.70