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 $95.67   6.469%   $101.8589   $101.86   $101.85   $101.90  
  Purchase #2 $214.42   4.822%   $224.7593   $224.76   $224.75   $224.80  
  Purchase #3 $85.81   4.454%   $89.632   $89.63   $89.65   $89.60  
  Purchase #4 $246.96   4.246%   $257.4459   $257.45   $257.45   $257.40  
  Purchase #5 $199.60   3.227%   $206.0411   $206.04   $206.05   $206.00  
  Purchase #6 $104.52   4.217%   $108.9276   $108.93   $108.95   $108.90  
  Purchase #7 $148.91   5.216%   $156.6771   $156.68   $156.70   $156.70  
  7 purchase totals = $1,095.89       $1,145.3419   $1,145.35   $1,145.40   $1,145.30