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 $62.73   7.767%   $67.6022   $67.60   $67.60   $67.60  
  Purchase #2 $124.58   8.524%   $135.1992   $135.20   $135.20   $135.20  
  Purchase #3 $209.59   10.508%   $231.6137   $231.61   $231.60   $231.60  
  Purchase #4 $216.53   4.672%   $226.6463   $226.65   $226.65   $226.60  
  Purchase #5 $81.25   8.262%   $87.9629   $87.96   $87.95   $88.00  
  Purchase #6 $69.35   4.720%   $72.6233   $72.62   $72.60   $72.60  
  Purchase #7 $69.62   5.383%   $73.3676   $73.37   $73.35   $73.40  
  7 purchase totals = $833.65       $895.0152   $895.01   $894.95   $895.00