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 $58.84   4.561%   $61.5237   $61.52   $61.50   $61.50  
  Purchase #2 $224.58   12.522%   $252.7019   $252.70   $252.70   $252.70  
  Purchase #3 $94.68   12.503%   $106.5178   $106.52   $106.50   $106.50  
  Purchase #4 $42.71   12.826%   $48.188   $48.19   $48.20   $48.20  
  Purchase #5 $246.78   4.269%   $257.315   $257.32   $257.30   $257.30  
  Purchase #6 $244.81   10.174%   $269.717   $269.72   $269.70   $269.70  
  Purchase #7 $77.66   11.577%   $86.6507   $86.65   $86.65   $86.70  
  7 purchase totals = $990.06       $1,082.6141   $1,082.62   $1,082.55   $1,082.60