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 $244.75   7.445%   $262.9716   $262.97   $262.95   $263.00  
  Purchase #2 $58.87   5.178%   $61.9183   $61.92   $61.90   $61.90  
  Purchase #3 $26.96   3.398%   $27.8761   $27.88   $27.90   $27.90  
  Purchase #4 $32.37   9.530%   $35.4549   $35.45   $35.45   $35.50  
  Purchase #5 $237.98   6.568%   $253.6105   $253.61   $253.60   $253.60  
  Purchase #6 $179.37   10.169%   $197.6101   $197.61   $197.60   $197.60  
  Purchase #7 $27.56   4.560%   $28.8167   $28.82   $28.80   $28.80  
  7 purchase totals = $807.86       $868.2582   $868.26   $868.20   $868.30