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 $155.53   3.264%   $160.6065   $160.61   $160.60   $160.60  
  Purchase #2 $195.93   10.232%   $215.9776   $215.98   $216.00   $216.00  
  Purchase #3 $92.94   6.554%   $99.0313   $99.03   $99.05   $99.00  
  Purchase #4 $69.58   10.550%   $76.9207   $76.92   $76.90   $76.90  
  Purchase #5 $204.63   13.359%   $231.9665   $231.97   $231.95   $232.00  
  Purchase #6 $245.46   11.439%   $273.5382   $273.54   $273.55   $273.50  
  Purchase #7 $50.53   4.382%   $52.7442   $52.74   $52.75   $52.70  
  7 purchase totals = $1,014.60       $1,110.7850   $1,110.79   $1,110.80   $1,110.70