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 $200.84   3.814%   $208.5   $208.50   $208.50   $208.50  
  Purchase #2 $116.46   8.722%   $126.6176   $126.62   $126.60   $126.60  
  Purchase #3 $148.39   3.588%   $153.7142   $153.71   $153.70   $153.70  
  Purchase #4 $90.92   3.276%   $93.8985   $93.90   $93.90   $93.90  
  Purchase #5 $59.44   11.445%   $66.2429   $66.24   $66.25   $66.20  
  Purchase #6 $244.68   5.427%   $257.9588   $257.96   $257.95   $258.00  
  Purchase #7 $161.31   4.265%   $168.1899   $168.19   $168.20   $168.20  
  7 purchase totals = $1,022.04       $1,075.1219   $1,075.12   $1,075.10   $1,075.10