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 $63.70   8.717%   $69.2527   $69.25   $69.25   $69.30  
  Purchase #2 $179.89   13.760%   $204.6429   $204.64   $204.65   $204.60  
  Purchase #3 $153.42   10.711%   $169.8528   $169.85   $169.85   $169.90  
  Purchase #4 $90.43   8.631%   $98.235   $98.24   $98.25   $98.20  
  Purchase #5 $210.40   4.874%   $220.6549   $220.65   $220.65   $220.70  
  Purchase #6 $222.79   4.493%   $232.8   $232.80   $232.80   $232.80  
  Purchase #7 $183.55   9.226%   $200.4843   $200.48   $200.50   $200.50  
  7 purchase totals = $1,104.18       $1,195.9226   $1,195.91   $1,195.95   $1,196.00