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 $41.68   11.802%   $46.5991   $46.60   $46.60   $46.60  
  Purchase #2 $169.32   6.404%   $180.1633   $180.16   $180.15   $180.20  
  Purchase #3 $66.88   6.385%   $71.1503   $71.15   $71.15   $71.20  
  Purchase #4 $224.28   7.264%   $240.5717   $240.57   $240.55   $240.60  
  Purchase #5 $122.49   11.224%   $136.2383   $136.24   $136.25   $136.20  
  Purchase #6 $73.95   5.178%   $77.7791   $77.78   $77.80   $77.80  
  Purchase #7 $15.47   6.685%   $16.5042   $16.50   $16.50   $16.50  
  7 purchase totals = $714.07       $769.0060   $769.00   $769.00   $769.10