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 $68.26   12.236%   $76.6123   $76.61   $76.60   $76.60  
  Purchase #2 $250.25   6.653%   $266.8991   $266.90   $266.90   $266.90  
  Purchase #3 $92.41   11.870%   $103.3791   $103.38   $103.40   $103.40  
  Purchase #4 $186.99   12.236%   $209.8701   $209.87   $209.85   $209.90  
  Purchase #5 $209.45   3.240%   $216.2362   $216.24   $216.25   $216.20  
  Purchase #6 $217.44   5.862%   $230.1863   $230.19   $230.20   $230.20  
  Purchase #7 $22.78   7.859%   $24.5703   $24.57   $24.55   $24.60  
  7 purchase totals = $1,047.58       $1,127.7534   $1,127.76   $1,127.75   $1,127.80