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 $207.46   5.232%   $218.3143   $218.31   $218.30   $218.30  
  Purchase #2 $195.55   8.263%   $211.7083   $211.71   $211.70   $211.70  
  Purchase #3 $108.47   6.860%   $115.911   $115.91   $115.90   $115.90  
  Purchase #4 $238.95   10.675%   $264.4579   $264.46   $264.45   $264.50  
  Purchase #5 $75.36   4.727%   $78.9223   $78.92   $78.90   $78.90  
  Purchase #6 $179.46   12.110%   $201.1926   $201.19   $201.20   $201.20  
  Purchase #7 $109.27   4.404%   $114.0823   $114.08   $114.10   $114.10  
  7 purchase totals = $1,114.52       $1,204.5887   $1,204.58   $1,204.55   $1,204.60