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 $196.58   7.671%   $211.6597   $211.66   $211.65   $211.70  
  Purchase #2 $219.43   10.839%   $243.214   $243.21   $243.20   $243.20  
  Purchase #3 $50.67   13.701%   $57.6123   $57.61   $57.60   $57.60  
  Purchase #4 $199.49   11.477%   $222.3855   $222.39   $222.40   $222.40  
  Purchase #5 $211.25   8.551%   $229.314   $229.31   $229.30   $229.30  
  Purchase #6 $196.69   3.504%   $203.582   $203.58   $203.60   $203.60  
  Purchase #7 $92.60   9.477%   $101.3757   $101.38   $101.40   $101.40  
  7 purchase totals = $1,166.71       $1,269.1432   $1,269.14   $1,269.15   $1,269.20