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 $160.61   13.475%   $182.2522   $182.25   $182.25   $182.30  
  Purchase #2 $202.42   9.470%   $221.5892   $221.59   $221.60   $221.60  
  Purchase #3 $52.26   4.423%   $54.5715   $54.57   $54.55   $54.60  
  Purchase #4 $164.39   3.170%   $169.6012   $169.60   $169.60   $169.60  
  Purchase #5 $148.27   3.484%   $153.4357   $153.44   $153.45   $153.40  
  Purchase #6 $131.76   4.295%   $137.4191   $137.42   $137.40   $137.40  
  Purchase #7 $108.45   13.228%   $122.7958   $122.80   $122.80   $122.80  
  7 purchase totals = $968.16       $1,041.6647   $1,041.67   $1,041.65   $1,041.70