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 $48.46   9.270%   $52.9522   $52.95   $52.95   $53.00  
  Purchase #2 $223.95   12.789%   $252.591   $252.59   $252.60   $252.60  
  Purchase #3 $126.78   5.109%   $133.2572   $133.26   $133.25   $133.30  
  Purchase #4 $81.75   6.361%   $86.9501   $86.95   $86.95   $87.00  
  Purchase #5 $138.57   9.330%   $151.4986   $151.50   $151.50   $151.50  
  Purchase #6 $101.47   3.161%   $104.6775   $104.68   $104.70   $104.70  
  Purchase #7 $246.61   13.366%   $279.5719   $279.57   $279.55   $279.60  
  7 purchase totals = $967.59       $1,061.4985   $1,061.50   $1,061.50   $1,061.70