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 $117.45   4.130%   $122.3007   $122.30   $122.30   $122.30  
  Purchase #2 $119.52   5.189%   $125.7219   $125.72   $125.70   $125.70  
  Purchase #3 $156.86   12.237%   $176.055   $176.06   $176.05   $176.10  
  Purchase #4 $182.82   5.819%   $193.4583   $193.46   $193.45   $193.50  
  Purchase #5 $226.38   5.679%   $239.2361   $239.24   $239.25   $239.20  
  Purchase #6 $226.79   9.183%   $247.6161   $247.62   $247.60   $247.60  
  Purchase #7 $28.29   6.552%   $30.1436   $30.14   $30.15   $30.10  
  7 purchase totals = $1,058.11       $1,134.5317   $1,134.54   $1,134.50   $1,134.50