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 $38.90   10.637%   $43.0378   $43.04   $43.05   $43.00  
  Purchase #2 $203.61   7.328%   $218.5305   $218.53   $218.55   $218.50  
  Purchase #3 $230.79   7.611%   $248.3554   $248.36   $248.35   $248.40  
  Purchase #4 $191.95   9.200%   $209.6094   $209.61   $209.60   $209.60  
  Purchase #5 $63.78   4.566%   $66.6922   $66.69   $66.70   $66.70  
  Purchase #6 $182.83   11.800%   $204.4039   $204.40   $204.40   $204.40  
  Purchase #7 $242.52   9.160%   $264.7348   $264.73   $264.75   $264.70  
  7 purchase totals = $1,154.38       $1,255.3640   $1,255.36   $1,255.40   $1,255.30