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 $163.65   7.728%   $176.2969   $176.30   $176.30   $176.30  
  Purchase #2 $238.32   11.693%   $266.1868   $266.19   $266.20   $266.20  
  Purchase #3 $168.30   12.625%   $189.5479   $189.55   $189.55   $189.50  
  Purchase #4 $245.99   3.430%   $254.4275   $254.43   $254.45   $254.40  
  Purchase #5 $157.56   12.691%   $177.5559   $177.56   $177.55   $177.60  
  Purchase #6 $164.36   6.818%   $175.5661   $175.57   $175.55   $175.60  
  Purchase #7 $211.91   8.540%   $230.0071   $230.01   $230.00   $230.00  
  7 purchase totals = $1,350.09       $1,469.5882   $1,469.61   $1,469.60   $1,469.60