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 $62.66   11.649%   $69.9593   $69.96   $69.95   $70.00  
  Purchase #2 $102.52   13.737%   $116.6032   $116.60   $116.60   $116.60  
  Purchase #3 $207.48   13.635%   $235.7699   $235.77   $235.75   $235.80  
  Purchase #4 $211.54   8.621%   $229.7769   $229.78   $229.80   $229.80  
  Purchase #5 $192.70   13.804%   $219.3003   $219.30   $219.30   $219.30  
  Purchase #6 $101.71   10.217%   $112.1017   $112.10   $112.10   $112.10  
  Purchase #7 $171.83   12.816%   $193.8517   $193.85   $193.85   $193.90  
  7 purchase totals = $1,050.44       $1,177.3630   $1,177.36   $1,177.35   $1,177.50