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 $177.59   10.346%   $195.9635   $195.96   $195.95   $196.00  
  Purchase #2 $68.31   3.576%   $70.7528   $70.75   $70.75   $70.80  
  Purchase #3 $103.62   7.833%   $111.7366   $111.74   $111.75   $111.70  
  Purchase #4 $92.48   9.608%   $101.3655   $101.37   $101.35   $101.40  
  Purchase #5 $119.35   6.448%   $127.0457   $127.05   $127.05   $127.00  
  Purchase #6 $30.94   6.268%   $32.8793   $32.88   $32.90   $32.90  
  Purchase #7 $208.93   12.315%   $234.6597   $234.66   $234.65   $234.70  
  7 purchase totals = $801.22       $874.4031   $874.41   $874.40   $874.50