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 $235.44   4.764%   $246.6564   $246.66   $246.65   $246.70  
  Purchase #2 $122.69   3.182%   $126.594   $126.59   $126.60   $126.60  
  Purchase #3 $168.52   9.809%   $185.0501   $185.05   $185.05   $185.10  
  Purchase #4 $68.92   11.114%   $76.5798   $76.58   $76.60   $76.60  
  Purchase #5 $166.68   8.873%   $181.4695   $181.47   $181.45   $181.50  
  Purchase #6 $215.65   12.273%   $242.1167   $242.12   $242.10   $242.10  
  Purchase #7 $168.39   8.575%   $182.8294   $182.83   $182.85   $182.80  
  7 purchase totals = $1,146.29       $1,241.2959   $1,241.30   $1,241.30   $1,241.40