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 $88.95   8.577%   $96.5792   $96.58   $96.60   $96.60  
  Purchase #2 $170.79   8.427%   $185.1825   $185.18   $185.20   $185.20  
  Purchase #3 $10.46   3.398%   $10.8154   $10.82   $10.80   $10.80  
  Purchase #4 $67.57   8.724%   $73.4648   $73.46   $73.45   $73.50  
  Purchase #5 $192.97   4.828%   $202.2866   $202.29   $202.30   $202.30  
  Purchase #6 $200.46   10.289%   $221.0853   $221.09   $221.10   $221.10  
  Purchase #7 $165.69   6.231%   $176.0141   $176.01   $176.00   $176.00  
  7 purchase totals = $896.89       $965.4279   $965.43   $965.45   $965.50