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 $65.64   5.535%   $69.2732   $69.27   $69.25   $69.30  
  Purchase #2 $202.78   5.385%   $213.6997   $213.70   $213.70   $213.70  
  Purchase #3 $164.73   11.559%   $183.7711   $183.77   $183.75   $183.80  
  Purchase #4 $23.89   9.654%   $26.1963   $26.20   $26.20   $26.20  
  Purchase #5 $239.86   5.156%   $252.2272   $252.23   $252.25   $252.20  
  Purchase #6 $132.58   7.306%   $142.2663   $142.27   $142.25   $142.30  
  Purchase #7 $127.58   3.528%   $132.081   $132.08   $132.10   $132.10  
  7 purchase totals = $957.06       $1,019.5148   $1,019.52   $1,019.50   $1,019.60