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 $153.42   8.678%   $166.7338   $166.73   $166.75   $166.70  
  Purchase #2 $54.93   12.846%   $61.9863   $61.99   $62.00   $62.00  
  Purchase #3 $32.56   5.618%   $34.3892   $34.39   $34.40   $34.40  
  Purchase #4 $164.45   3.711%   $170.5527   $170.55   $170.55   $170.60  
  Purchase #5 $235.44   11.519%   $262.5603   $262.56   $262.55   $262.60  
  Purchase #6 $216.90   8.130%   $234.534   $234.53   $234.55   $234.50  
  Purchase #7 $114.93   13.279%   $130.1916   $130.19   $130.20   $130.20  
  7 purchase totals = $972.63       $1,060.9479   $1,060.94   $1,061.00   $1,061.00