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 $206.95   13.305%   $234.4847   $234.48   $234.50   $234.50  
  Purchase #2 $180.89   5.422%   $190.6979   $190.70   $190.70   $190.70  
  Purchase #3 $210.94   6.232%   $224.0858   $224.09   $224.10   $224.10  
  Purchase #4 $86.95   9.444%   $95.1616   $95.16   $95.15   $95.20  
  Purchase #5 $23.29   12.106%   $26.1095   $26.11   $26.10   $26.10  
  Purchase #6 $233.55   11.282%   $259.8991   $259.90   $259.90   $259.90  
  Purchase #7 $17.96   8.659%   $19.5152   $19.52   $19.50   $19.50  
  7 purchase totals = $960.53       $1,049.9538   $1,049.96   $1,049.95   $1,050.00