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 $203.49   3.698%   $211.0151   $211.02   $211.00   $211.00  
  Purchase #2 $214.90   11.821%   $240.3033   $240.30   $240.30   $240.30  
  Purchase #3 $40.83   13.599%   $46.3825   $46.38   $46.40   $46.40  
  Purchase #4 $155.32   13.126%   $175.7073   $175.71   $175.70   $175.70  
  Purchase #5 $192.25   6.791%   $205.3057   $205.31   $205.30   $205.30  
  Purchase #6 $183.56   13.135%   $207.6706   $207.67   $207.65   $207.70  
  Purchase #7 $228.96   7.691%   $246.5693   $246.57   $246.55   $246.60  
  7 purchase totals = $1,219.31       $1,332.9538   $1,332.96   $1,332.90   $1,333.00