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 $83.43   11.609%   $93.1154   $93.12   $93.10   $93.10  
  Purchase #2 $209.84   12.622%   $236.326   $236.33   $236.35   $236.30  
  Purchase #3 $69.81   8.858%   $75.9938   $75.99   $76.00   $76.00  
  Purchase #4 $68.69   10.645%   $76.0021   $76.00   $76.00   $76.00  
  Purchase #5 $125.32   3.348%   $129.5157   $129.52   $129.50   $129.50  
  Purchase #6 $242.63   8.608%   $263.5156   $263.52   $263.50   $263.50  
  Purchase #7 $219.94   7.603%   $236.662   $236.66   $236.65   $236.70  
  7 purchase totals = $1,019.66       $1,111.1306   $1,111.14   $1,111.10   $1,111.10