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 $129.78   3.406%   $134.2003   $134.20   $134.20   $134.20  
  Purchase #2 $186.30   10.845%   $206.5042   $206.50   $206.50   $206.50  
  Purchase #3 $247.90   8.261%   $268.379   $268.38   $268.40   $268.40  
  Purchase #4 $48.69   7.759%   $52.4679   $52.47   $52.45   $52.50  
  Purchase #5 $118.52   3.448%   $122.6066   $122.61   $122.60   $122.60  
  Purchase #6 $213.64   10.771%   $236.6512   $236.65   $236.65   $236.70  
  Purchase #7 $87.80   8.449%   $95.2182   $95.22   $95.20   $95.20  
  7 purchase totals = $1,032.63       $1,116.0274   $1,116.03   $1,116.00   $1,116.10