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 $208.98   7.510%   $224.6744   $224.67   $224.65   $224.70  
  Purchase #2 $187.31   3.202%   $193.3077   $193.31   $193.30   $193.30  
  Purchase #3 $16.39   6.408%   $17.4403   $17.44   $17.45   $17.40  
  Purchase #4 $65.41   4.330%   $68.2423   $68.24   $68.25   $68.20  
  Purchase #5 $156.68   7.521%   $168.4639   $168.46   $168.45   $168.50  
  Purchase #6 $185.94   6.813%   $198.6081   $198.61   $198.60   $198.60  
  Purchase #7 $22.63   8.807%   $24.623   $24.62   $24.60   $24.60  
  7 purchase totals = $843.34       $895.3597   $895.35   $895.30   $895.30