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 $61.52   13.210%   $69.6468   $69.65   $69.65   $69.60  
  Purchase #2 $105.43   10.374%   $116.3673   $116.37   $116.35   $116.40  
  Purchase #3 $163.72   12.741%   $184.5796   $184.58   $184.60   $184.60  
  Purchase #4 $11.94   6.874%   $12.7608   $12.76   $12.75   $12.80  
  Purchase #5 $46.59   8.573%   $50.5842   $50.58   $50.60   $50.60  
  Purchase #6 $98.71   4.354%   $103.0078   $103.01   $103.00   $103.00  
  Purchase #7 $178.86   9.406%   $195.6836   $195.68   $195.70   $195.70  
  7 purchase totals = $666.77       $732.6301   $732.63   $732.65   $732.70