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 $208.32   12.861%   $235.112   $235.11   $235.10   $235.10  
  Purchase #2 $188.48   5.491%   $198.8294   $198.83   $198.85   $198.80  
  Purchase #3 $65.68   12.173%   $73.6752   $73.68   $73.70   $73.70  
  Purchase #4 $160.81   5.378%   $169.4584   $169.46   $169.45   $169.50  
  Purchase #5 $134.52   9.689%   $147.5536   $147.55   $147.55   $147.60  
  Purchase #6 $34.67   11.697%   $38.7253   $38.73   $38.75   $38.70  
  Purchase #7 $31.55   3.169%   $32.5498   $32.55   $32.55   $32.50  
  7 purchase totals = $824.03       $895.9037   $895.91   $895.95   $895.90