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 $64.93   7.153%   $69.5744   $69.57   $69.55   $69.60  
  Purchase #2 $247.62   6.153%   $262.8561   $262.86   $262.85   $262.90  
  Purchase #3 $57.97   6.702%   $61.8551   $61.86   $61.85   $61.90  
  Purchase #4 $74.81   6.701%   $79.823   $79.82   $79.80   $79.80  
  Purchase #5 $153.37   5.207%   $161.356   $161.36   $161.35   $161.40  
  Purchase #6 $56.81   12.185%   $63.7323   $63.73   $63.75   $63.70  
  Purchase #7 $60.30   4.522%   $63.0268   $63.03   $63.05   $63.00  
  7 purchase totals = $715.81       $762.2237   $762.23   $762.20   $762.30