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 $141.29   8.500%   $153.2997   $153.30   $153.30   $153.30  
  Purchase #2 $241.43   8.514%   $261.9854   $261.99   $262.00   $262.00  
  Purchase #3 $208.85   13.791%   $237.6525   $237.65   $237.65   $237.70  
  Purchase #4 $74.37   7.783%   $80.1582   $80.16   $80.15   $80.20  
  Purchase #5 $8.56   12.138%   $9.599   $9.60   $9.60   $9.60  
  Purchase #6 $118.85   6.325%   $126.3673   $126.37   $126.35   $126.40  
  Purchase #7 $202.34   5.250%   $212.9629   $212.96   $212.95   $213.00  
  7 purchase totals = $995.69       $1,082.0250   $1,082.03   $1,082.00   $1,082.20