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 $114.39   9.535%   $125.2971   $125.30   $125.30   $125.30  
  Purchase #2 $90.43   4.343%   $94.3574   $94.36   $94.35   $94.40  
  Purchase #3 $65.77   10.517%   $72.687   $72.69   $72.70   $72.70  
  Purchase #4 $98.94   8.773%   $107.62   $107.62   $107.60   $107.60  
  Purchase #5 $63.76   3.263%   $65.8405   $65.84   $65.85   $65.80  
  Purchase #6 $77.30   11.357%   $86.079   $86.08   $86.10   $86.10  
  Purchase #7 $61.83   8.556%   $67.1202   $67.12   $67.10   $67.10  
  7 purchase totals = $572.42       $619.0012   $619.01   $619.00   $619.00