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 $174.85   13.553%   $198.5474   $198.55   $198.55   $198.50  
  Purchase #2 $201.55   6.822%   $215.2997   $215.30   $215.30   $215.30  
  Purchase #3 $120.75   4.342%   $125.993   $125.99   $126.00   $126.00  
  Purchase #4 $175.29   5.599%   $185.1045   $185.10   $185.10   $185.10  
  Purchase #5 $149.83   12.531%   $168.6052   $168.61   $168.60   $168.60  
  Purchase #6 $62.37   3.666%   $64.6565   $64.66   $64.65   $64.70  
  Purchase #7 $101.62   4.281%   $105.9704   $105.97   $105.95   $106.00  
  7 purchase totals = $986.26       $1,064.1767   $1,064.18   $1,064.15   $1,064.20