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 $202.40   4.254%   $211.0101   $211.01   $211.00   $211.00  
  Purchase #2 $197.87   13.499%   $224.5805   $224.58   $224.60   $224.60  
  Purchase #3 $55.96   13.298%   $63.4016   $63.40   $63.40   $63.40  
  Purchase #4 $62.74   5.306%   $66.069   $66.07   $66.05   $66.10  
  Purchase #5 $178.74   9.293%   $195.3503   $195.35   $195.35   $195.40  
  Purchase #6 $160.66   10.498%   $177.5261   $177.53   $177.55   $177.50  
  Purchase #7 $61.28   12.493%   $68.9357   $68.94   $68.95   $68.90  
  7 purchase totals = $919.65       $1,006.8733   $1,006.88   $1,006.90   $1,006.90