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 $60.95   5.758%   $64.4595   $64.46   $64.45   $64.50  
  Purchase #2 $67.85   5.476%   $71.5655   $71.57   $71.55   $71.60  
  Purchase #3 $221.58   3.452%   $229.2289   $229.23   $229.25   $229.20  
  Purchase #4 $209.40   9.477%   $229.2448   $229.24   $229.25   $229.20  
  Purchase #5 $196.37   3.751%   $203.7358   $203.74   $203.75   $203.70  
  Purchase #6 $62.58   3.171%   $64.5644   $64.56   $64.55   $64.60  
  Purchase #7 $249.71   3.397%   $258.1926   $258.19   $258.20   $258.20  
  7 purchase totals = $1,068.44       $1,120.9915   $1,120.99   $1,121.00   $1,121.00