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 $67.51   8.104%   $72.981   $72.98   $73.00   $73.00  
  Purchase #2 $206.44   13.738%   $234.8007   $234.80   $234.80   $234.80  
  Purchase #3 $240.82   7.859%   $259.746   $259.75   $259.75   $259.70  
  Purchase #4 $22.63   3.284%   $23.3732   $23.37   $23.35   $23.40  
  Purchase #5 $43.27   6.291%   $45.9921   $45.99   $46.00   $46.00  
  Purchase #6 $146.85   9.838%   $161.2971   $161.30   $161.30   $161.30  
  Purchase #7 $82.55   8.216%   $89.3323   $89.33   $89.35   $89.30  
  7 purchase totals = $810.07       $887.5224   $887.52   $887.55   $887.50