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 $192.27   11.591%   $214.556   $214.56   $214.55   $214.60  
  Purchase #2 $222.41   9.509%   $243.559   $243.56   $243.55   $243.60  
  Purchase #3 $85.32   10.155%   $93.9842   $93.98   $94.00   $94.00  
  Purchase #4 $30.40   13.555%   $34.5207   $34.52   $34.50   $34.50  
  Purchase #5 $102.67   7.675%   $110.5499   $110.55   $110.55   $110.50  
  Purchase #6 $32.45   4.734%   $33.9862   $33.99   $34.00   $34.00  
  Purchase #7 $126.86   4.845%   $133.0064   $133.01   $133.00   $133.00  
  7 purchase totals = $792.38       $864.1624   $864.17   $864.15   $864.20