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 $169.65   13.801%   $193.0634   $193.06   $193.05   $193.10  
  Purchase #2 $43.96   6.233%   $46.7   $46.70   $46.70   $46.70  
  Purchase #3 $192.57   10.202%   $212.216   $212.22   $212.20   $212.20  
  Purchase #4 $165.62   6.271%   $176.006   $176.01   $176.00   $176.00  
  Purchase #5 $43.35   8.479%   $47.0256   $47.03   $47.05   $47.00  
  Purchase #6 $143.50   10.534%   $158.6163   $158.62   $158.60   $158.60  
  Purchase #7 $59.91   6.167%   $63.6046   $63.60   $63.60   $63.60  
  7 purchase totals = $818.56       $897.2319   $897.24   $897.20   $897.20