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 $195.95   8.470%   $212.547   $212.55   $212.55   $212.50  
  Purchase #2 $58.66   3.826%   $60.9043   $60.90   $60.90   $60.90  
  Purchase #3 $82.68   5.168%   $86.9529   $86.95   $86.95   $87.00  
  Purchase #4 $117.93   9.608%   $129.2607   $129.26   $129.25   $129.30  
  Purchase #5 $221.50   4.266%   $230.9492   $230.95   $230.95   $230.90  
  Purchase #6 $66.54   11.829%   $74.411   $74.41   $74.40   $74.40  
  Purchase #7 $70.48   4.482%   $73.6389   $73.64   $73.65   $73.60  
  7 purchase totals = $813.74       $868.6640   $868.66   $868.65   $868.60