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 $119.84   10.762%   $132.7372   $132.74   $132.75   $132.70  
  Purchase #2 $142.79   3.179%   $147.3293   $147.33   $147.35   $147.30  
  Purchase #3 $243.97   7.696%   $262.7459   $262.75   $262.75   $262.70  
  Purchase #4 $72.25   3.269%   $74.6119   $74.61   $74.60   $74.60  
  Purchase #5 $132.76   4.619%   $138.8922   $138.89   $138.90   $138.90  
  Purchase #6 $84.77   11.649%   $94.6449   $94.64   $94.65   $94.60  
  Purchase #7 $230.58   5.673%   $243.6608   $243.66   $243.65   $243.70  
  7 purchase totals = $1,026.96       $1,094.6222   $1,094.62   $1,094.65   $1,094.50