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 $55.38   11.200%   $61.5826   $61.58   $61.60   $61.60  
  Purchase #2 $187.56   12.295%   $210.6205   $210.62   $210.60   $210.60  
  Purchase #3 $224.81   13.445%   $255.0357   $255.04   $255.05   $255.00  
  Purchase #4 $36.44   7.595%   $39.2076   $39.21   $39.20   $39.20  
  Purchase #5 $245.91   4.215%   $256.2751   $256.28   $256.30   $256.30  
  Purchase #6 $232.74   12.692%   $262.2794   $262.28   $262.30   $262.30  
  Purchase #7 $45.99   3.647%   $47.6673   $47.67   $47.65   $47.70  
  7 purchase totals = $1,028.83       $1,132.6682   $1,132.68   $1,132.70   $1,132.70