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 $114.65   4.295%   $119.5742   $119.57   $119.55   $119.60  
  Purchase #2 $233.32   12.429%   $262.3193   $262.32   $262.30   $262.30  
  Purchase #3 $5.49   10.158%   $6.0477   $6.05   $6.05   $6.00  
  Purchase #4 $142.58   3.724%   $147.8897   $147.89   $147.90   $147.90  
  Purchase #5 $95.33   11.301%   $106.1032   $106.10   $106.10   $106.10  
  Purchase #6 $109.27   11.303%   $121.6208   $121.62   $121.60   $121.60  
  Purchase #7 $238.64   7.332%   $256.1371   $256.14   $256.15   $256.10  
  7 purchase totals = $939.28       $1,019.6920   $1,019.69   $1,019.65   $1,019.60