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 $58.26   8.484%   $63.2028   $63.20   $63.20   $63.20  
  Purchase #2 $177.52   10.153%   $195.5436   $195.54   $195.55   $195.50  
  Purchase #3 $23.58   12.773%   $26.5919   $26.59   $26.60   $26.60  
  Purchase #4 $132.46   9.802%   $145.4437   $145.44   $145.45   $145.40  
  Purchase #5 $129.56   9.122%   $141.3785   $141.38   $141.40   $141.40  
  Purchase #6 $33.74   6.580%   $35.9601   $35.96   $35.95   $36.00  
  Purchase #7 $147.44   6.400%   $156.8762   $156.88   $156.90   $156.90  
  7 purchase totals = $702.56       $764.9968   $764.99   $765.05   $765.00