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 $182.40   5.275%   $192.0216   $192.02   $192.00   $192.00  
  Purchase #2 $72.59   5.211%   $76.3727   $76.37   $76.35   $76.40  
  Purchase #3 $230.37   5.435%   $242.8906   $242.89   $242.90   $242.90  
  Purchase #4 $184.56   5.241%   $194.2328   $194.23   $194.25   $194.20  
  Purchase #5 $88.70   11.121%   $98.5643   $98.56   $98.55   $98.60  
  Purchase #6 $104.38   4.126%   $108.6867   $108.69   $108.70   $108.70  
  Purchase #7 $217.85   11.546%   $243.003   $243.00   $243.00   $243.00  
  7 purchase totals = $1,080.85       $1,155.7717   $1,155.76   $1,155.75   $1,155.80