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 $58.58   5.388%   $61.7363   $61.74   $61.75   $61.70  
  Purchase #2 $237.99   4.783%   $249.3731   $249.37   $249.35   $249.40  
  Purchase #3 $97.69   5.630%   $103.1899   $103.19   $103.20   $103.20  
  Purchase #4 $159.30   11.867%   $178.2041   $178.20   $178.20   $178.20  
  Purchase #5 $239.52   13.826%   $272.636   $272.64   $272.65   $272.60  
  Purchase #6 $123.54   4.744%   $129.4007   $129.40   $129.40   $129.40  
  Purchase #7 $63.58   10.183%   $70.0544   $70.05   $70.05   $70.10  
  7 purchase totals = $980.20       $1,064.5945   $1,064.59   $1,064.60   $1,064.60