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 $86.66   10.807%   $96.0253   $96.03   $96.05   $96.00  
  Purchase #2 $191.74   4.503%   $200.3741   $200.37   $200.35   $200.40  
  Purchase #3 $147.78   5.769%   $156.3054   $156.31   $156.30   $156.30  
  Purchase #4 $42.67   9.595%   $46.7642   $46.76   $46.75   $46.80  
  Purchase #5 $26.62   9.758%   $29.2176   $29.22   $29.20   $29.20  
  Purchase #6 $235.44   4.312%   $245.5922   $245.59   $245.60   $245.60  
  Purchase #7 $160.43   6.678%   $171.1435   $171.14   $171.15   $171.10  
  7 purchase totals = $891.34       $945.4223   $945.42   $945.40   $945.40