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 $63.30   13.527%   $71.8626   $71.86   $71.85   $71.90  
  Purchase #2 $195.92   11.151%   $217.767   $217.77   $217.75   $217.80  
  Purchase #3 $200.55   4.133%   $208.8387   $208.84   $208.85   $208.80  
  Purchase #4 $46.59   8.513%   $50.5562   $50.56   $50.55   $50.60  
  Purchase #5 $45.68   6.447%   $48.625   $48.63   $48.65   $48.60  
  Purchase #6 $151.48   3.188%   $156.3092   $156.31   $156.30   $156.30  
  Purchase #7 $195.54   7.326%   $209.8653   $209.87   $209.85   $209.90  
  7 purchase totals = $899.06       $963.8240   $963.84   $963.80   $963.90