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 $85.70   12.713%   $96.595   $96.60   $96.60   $96.60  
  Purchase #2 $197.63   11.585%   $220.5254   $220.53   $220.55   $220.50  
  Purchase #3 $240.63   8.115%   $260.1571   $260.16   $260.15   $260.20  
  Purchase #4 $49.57   12.245%   $55.6398   $55.64   $55.65   $55.60  
  Purchase #5 $104.86   8.627%   $113.9063   $113.91   $113.90   $113.90  
  Purchase #6 $126.93   5.595%   $134.0317   $134.03   $134.05   $134.00  
  Purchase #7 $175.49   10.851%   $194.5324   $194.53   $194.55   $194.50  
  7 purchase totals = $980.81       $1,075.3877   $1,075.40   $1,075.45   $1,075.30