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 $243.62   10.283%   $268.6714   $268.67   $268.65   $268.70  
  Purchase #2 $220.73   9.500%   $241.6994   $241.70   $241.70   $241.70  
  Purchase #3 $168.87   4.410%   $176.3172   $176.32   $176.30   $176.30  
  Purchase #4 $105.87   9.199%   $115.609   $115.61   $115.60   $115.60  
  Purchase #5 $147.49   6.115%   $156.509   $156.51   $156.50   $156.50  
  Purchase #6 $82.79   3.868%   $85.9923   $85.99   $86.00   $86.00  
  Purchase #7 $142.25   11.308%   $158.3356   $158.34   $158.35   $158.30  
  7 purchase totals = $1,111.62       $1,203.1339   $1,203.14   $1,203.10   $1,203.10