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 $88.76   4.715%   $92.945   $92.95   $92.95   $92.90  
  Purchase #2 $213.30   10.557%   $235.8181   $235.82   $235.80   $235.80  
  Purchase #3 $106.81   9.871%   $117.3532   $117.35   $117.35   $117.40  
  Purchase #4 $166.51   4.778%   $174.4658   $174.47   $174.45   $174.50  
  Purchase #5 $147.93   9.147%   $161.4612   $161.46   $161.45   $161.50  
  Purchase #6 $142.98   8.516%   $155.1562   $155.16   $155.15   $155.20  
  Purchase #7 $113.62   12.720%   $128.0725   $128.07   $128.05   $128.10  
  7 purchase totals = $979.91       $1,065.2720   $1,065.28   $1,065.20   $1,065.40