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 $59.54   5.408%   $62.7599   $62.76   $62.75   $62.80  
  Purchase #2 $46.68   11.758%   $52.1686   $52.17   $52.15   $52.20  
  Purchase #3 $176.74   13.308%   $200.2606   $200.26   $200.25   $200.30  
  Purchase #4 $180.99   6.157%   $192.1336   $192.13   $192.15   $192.10  
  Purchase #5 $137.25   11.726%   $153.3439   $153.34   $153.35   $153.30  
  Purchase #6 $213.80   8.788%   $232.5887   $232.59   $232.60   $232.60  
  Purchase #7 $169.98   7.542%   $182.7999   $182.80   $182.80   $182.80  
  7 purchase totals = $984.98       $1,076.0552   $1,076.05   $1,076.05   $1,076.10