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 $24.64   7.655%   $26.5262   $26.53   $26.55   $26.50  
  Purchase #2 $214.79   3.870%   $223.1024   $223.10   $223.10   $223.10  
  Purchase #3 $194.25   4.469%   $202.931   $202.93   $202.95   $202.90  
  Purchase #4 $199.42   8.632%   $216.6339   $216.63   $216.65   $216.60  
  Purchase #5 $31.25   9.352%   $34.1725   $34.17   $34.15   $34.20  
  Purchase #6 $167.98   6.721%   $179.2699   $179.27   $179.25   $179.30  
  Purchase #7 $157.64   11.313%   $175.4738   $175.47   $175.45   $175.50  
  7 purchase totals = $989.97       $1,058.1097   $1,058.10   $1,058.10   $1,058.10