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 $177.88   10.746%   $196.995   $197.00   $197.00   $197.00  
  Purchase #2 $226.58   7.330%   $243.1883   $243.19   $243.20   $243.20  
  Purchase #3 $58.85   6.508%   $62.68   $62.68   $62.70   $62.70  
  Purchase #4 $72.88   11.655%   $81.3742   $81.37   $81.35   $81.40  
  Purchase #5 $193.65   6.145%   $205.5498   $205.55   $205.55   $205.50  
  Purchase #6 $42.88   13.568%   $48.698   $48.70   $48.70   $48.70  
  Purchase #7 $47.25   13.369%   $53.5669   $53.57   $53.55   $53.60  
  7 purchase totals = $819.97       $892.0522   $892.06   $892.05   $892.10