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 $32.70   5.718%   $34.5698   $34.57   $34.55   $34.60  
  Purchase #2 $234.36   7.224%   $251.2902   $251.29   $251.30   $251.30  
  Purchase #3 $22.38   4.706%   $23.4332   $23.43   $23.45   $23.40  
  Purchase #4 $169.59   7.838%   $182.8825   $182.88   $182.90   $182.90  
  Purchase #5 $87.50   8.567%   $94.9961   $95.00   $95.00   $95.00  
  Purchase #6 $72.52   5.218%   $76.3041   $76.30   $76.30   $76.30  
  Purchase #7 $57.26   5.697%   $60.5221   $60.52   $60.50   $60.50  
  7 purchase totals = $676.31       $723.9980   $723.99   $724.00   $724.00