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 $208.96   3.818%   $216.9381   $216.94   $216.95   $216.90  
  Purchase #2 $163.71   3.690%   $169.7509   $169.75   $169.75   $169.80  
  Purchase #3 $149.51   4.587%   $156.368   $156.37   $156.35   $156.40  
  Purchase #4 $23.86   4.306%   $24.8874   $24.89   $24.90   $24.90  
  Purchase #5 $91.94   7.299%   $98.6507   $98.65   $98.65   $98.70  
  Purchase #6 $194.50   6.710%   $207.551   $207.55   $207.55   $207.60  
  Purchase #7 $58.93   13.844%   $67.0883   $67.09   $67.10   $67.10  
  7 purchase totals = $891.41       $941.2344   $941.24   $941.25   $941.40