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 $245.66   7.383%   $263.7971   $263.80   $263.80   $263.80  
  Purchase #2 $244.98   11.291%   $272.6407   $272.64   $272.65   $272.60  
  Purchase #3 $179.27   9.778%   $196.799   $196.80   $196.80   $196.80  
  Purchase #4 $71.59   9.214%   $78.1863   $78.19   $78.20   $78.20  
  Purchase #5 $214.30   4.874%   $224.745   $224.75   $224.75   $224.70  
  Purchase #6 $211.29   5.766%   $223.473   $223.47   $223.45   $223.50  
  Purchase #7 $49.90   13.439%   $56.6061   $56.61   $56.60   $56.60  
  7 purchase totals = $1,216.99       $1,316.2472   $1,316.26   $1,316.25   $1,316.20