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 $85.37   9.827%   $93.7593   $93.76   $93.75   $93.80  
  Purchase #2 $244.43   7.473%   $262.6963   $262.70   $262.70   $262.70  
  Purchase #3 $120.77   4.146%   $125.7771   $125.78   $125.80   $125.80  
  Purchase #4 $65.60   4.322%   $68.4352   $68.44   $68.45   $68.40  
  Purchase #5 $63.34   9.554%   $69.3915   $69.39   $69.40   $69.40  
  Purchase #6 $93.85   13.571%   $106.5864   $106.59   $106.60   $106.60  
  Purchase #7 $5.92   3.338%   $6.1176   $6.12   $6.10   $6.10  
  7 purchase totals = $679.28       $732.7634   $732.78   $732.80   $732.80