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 $163.85   8.267%   $177.3955   $177.40   $177.40   $177.40  
  Purchase #2 $216.45   13.627%   $245.9456   $245.95   $245.95   $245.90  
  Purchase #3 $210.69   10.416%   $232.6355   $232.64   $232.65   $232.60  
  Purchase #4 $33.75   4.765%   $35.3582   $35.36   $35.35   $35.40  
  Purchase #5 $124.56   12.776%   $140.4738   $140.47   $140.45   $140.50  
  Purchase #6 $218.59   11.749%   $244.2721   $244.27   $244.25   $244.30  
  Purchase #7 $150.87   7.111%   $161.5984   $161.60   $161.60   $161.60  
  7 purchase totals = $1,118.76       $1,237.6791   $1,237.69   $1,237.65   $1,237.70