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 $148.98   12.771%   $168.0062   $168.01   $168.00   $168.00  
  Purchase #2 $206.99   5.174%   $217.6997   $217.70   $217.70   $217.70  
  Purchase #3 $200.26   6.527%   $213.331   $213.33   $213.35   $213.30  
  Purchase #4 $23.62   7.184%   $25.3169   $25.32   $25.30   $25.30  
  Purchase #5 $125.81   4.431%   $131.3846   $131.38   $131.40   $131.40  
  Purchase #6 $198.44   4.591%   $207.5504   $207.55   $207.55   $207.60  
  Purchase #7 $223.83   6.438%   $238.2402   $238.24   $238.25   $238.20  
  7 purchase totals = $1,127.93       $1,201.5290   $1,201.53   $1,201.55   $1,201.50