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 $58.53   9.287%   $63.9657   $63.97   $63.95   $64.00  
  Purchase #2 $179.27   9.323%   $195.9833   $195.98   $196.00   $196.00  
  Purchase #3 $175.36   10.524%   $193.8149   $193.81   $193.80   $193.80  
  Purchase #4 $141.87   11.700%   $158.4688   $158.47   $158.45   $158.50  
  Purchase #5 $216.67   8.322%   $234.7013   $234.70   $234.70   $234.70  
  Purchase #6 $199.93   3.137%   $206.2018   $206.20   $206.20   $206.20  
  Purchase #7 $212.47   9.118%   $231.843   $231.84   $231.85   $231.80  
  7 purchase totals = $1,184.10       $1,284.9788   $1,284.97   $1,284.95   $1,285.00