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 $89.46   6.831%   $95.571   $95.57   $95.55   $95.60  
  Purchase #2 $43.59   6.322%   $46.3458   $46.35   $46.35   $46.30  
  Purchase #3 $63.52   3.152%   $65.5222   $65.52   $65.50   $65.50  
  Purchase #4 $5.44   5.714%   $5.7508   $5.75   $5.75   $5.80  
  Purchase #5 $174.54   3.223%   $180.1654   $180.17   $180.15   $180.20  
  Purchase #6 $237.55   9.537%   $260.2051   $260.21   $260.20   $260.20  
  Purchase #7 $177.40   8.747%   $192.9172   $192.92   $192.90   $192.90  
  7 purchase totals = $791.50       $846.4775   $846.49   $846.40   $846.50