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 $243.64   5.767%   $257.6907   $257.69   $257.70   $257.70  
  Purchase #2 $24.58   5.115%   $25.8373   $25.84   $25.85   $25.80  
  Purchase #3 $52.85   11.508%   $58.932   $58.93   $58.95   $58.90  
  Purchase #4 $58.61   3.446%   $60.6297   $60.63   $60.65   $60.60  
  Purchase #5 $233.78   5.105%   $245.7145   $245.71   $245.70   $245.70  
  Purchase #6 $167.57   11.821%   $187.3784   $187.38   $187.40   $187.40  
  Purchase #7 $176.34   11.384%   $196.4145   $196.41   $196.40   $196.40  
  7 purchase totals = $957.37       $1,032.5971   $1,032.59   $1,032.65   $1,032.50