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 $67.29   5.646%   $71.0892   $71.09   $71.10   $71.10  
  Purchase #2 $116.42   5.350%   $122.6485   $122.65   $122.65   $122.60  
  Purchase #3 $81.99   5.704%   $86.6667   $86.67   $86.65   $86.70  
  Purchase #4 $141.47   5.111%   $148.7005   $148.70   $148.70   $148.70  
  Purchase #5 $247.97   12.715%   $279.4994   $279.50   $279.50   $279.50  
  Purchase #6 $233.25   9.299%   $254.9399   $254.94   $254.95   $254.90  
  Purchase #7 $149.94   7.755%   $161.5678   $161.57   $161.55   $161.60  
  7 purchase totals = $1,038.33       $1,125.1120   $1,125.12   $1,125.10   $1,125.10