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 $202.99   6.553%   $216.2919   $216.29   $216.30   $216.30  
  Purchase #2 $219.93   13.604%   $249.8493   $249.85   $249.85   $249.80  
  Purchase #3 $54.58   9.366%   $59.692   $59.69   $59.70   $59.70  
  Purchase #4 $209.85   4.860%   $220.0487   $220.05   $220.05   $220.00  
  Purchase #5 $12.57   11.813%   $14.0549   $14.05   $14.05   $14.10  
  Purchase #6 $215.76   4.685%   $225.8684   $225.87   $225.85   $225.90  
  Purchase #7 $237.29   5.337%   $249.9542   $249.95   $249.95   $250.00  
  7 purchase totals = $1,152.97       $1,235.7594   $1,235.75   $1,235.75   $1,235.80