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 $195.50   6.398%   $208.0081   $208.01   $208.00   $208.00  
  Purchase #2 $221.25   6.785%   $236.2618   $236.26   $236.25   $236.30  
  Purchase #3 $32.70   4.854%   $34.2873   $34.29   $34.30   $34.30  
  Purchase #4 $171.25   11.103%   $190.2639   $190.26   $190.25   $190.30  
  Purchase #5 $149.45   11.366%   $166.4365   $166.44   $166.45   $166.40  
  Purchase #6 $224.53   12.381%   $252.3291   $252.33   $252.35   $252.30  
  Purchase #7 $160.74   4.356%   $167.7418   $167.74   $167.75   $167.70  
  7 purchase totals = $1,155.42       $1,255.3285   $1,255.33   $1,255.35   $1,255.30