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 $126.73   13.408%   $143.722   $143.72   $143.70   $143.70  
  Purchase #2 $26.95   6.127%   $28.6012   $28.60   $28.60   $28.60  
  Purchase #3 $108.93   3.384%   $112.6162   $112.62   $112.60   $112.60  
  Purchase #4 $247.49   8.536%   $268.6157   $268.62   $268.60   $268.60  
  Purchase #5 $194.46   3.406%   $201.0833   $201.08   $201.10   $201.10  
  Purchase #6 $161.39   9.787%   $177.1852   $177.19   $177.20   $177.20  
  Purchase #7 $175.63   3.749%   $182.2144   $182.21   $182.20   $182.20  
  7 purchase totals = $1,041.58       $1,114.0380   $1,114.04   $1,114.00   $1,114.00