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 $182.64   6.833%   $195.1198   $195.12   $195.10   $195.10  
  Purchase #2 $32.49   3.645%   $33.6743   $33.67   $33.65   $33.70  
  Purchase #3 $150.66   13.767%   $171.4014   $171.40   $171.40   $171.40  
  Purchase #4 $212.70   10.143%   $234.2742   $234.27   $234.25   $234.30  
  Purchase #5 $61.62   7.867%   $66.4676   $66.47   $66.45   $66.50  
  Purchase #6 $41.98   12.531%   $47.2405   $47.24   $47.25   $47.20  
  Purchase #7 $142.58   3.212%   $147.1597   $147.16   $147.15   $147.20  
  7 purchase totals = $824.67       $895.3375   $895.33   $895.25   $895.40