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 $183.25   5.769%   $193.8217   $193.82   $193.80   $193.80  
  Purchase #2 $118.48   5.420%   $124.9016   $124.90   $124.90   $124.90  
  Purchase #3 $164.42   5.860%   $174.055   $174.06   $174.05   $174.10  
  Purchase #4 $63.58   4.117%   $66.1976   $66.20   $66.20   $66.20  
  Purchase #5 $50.72   3.173%   $52.3293   $52.33   $52.35   $52.30  
  Purchase #6 $164.98   4.863%   $173.003   $173.00   $173.00   $173.00  
  Purchase #7 $23.63   4.246%   $24.6333   $24.63   $24.65   $24.60  
  7 purchase totals = $769.06       $808.9415   $808.94   $808.95   $808.90