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 $191.92   5.362%   $202.2108   $202.21   $202.20   $202.20  
  Purchase #2 $114.36   4.832%   $119.8859   $119.89   $119.90   $119.90  
  Purchase #3 $29.88   7.396%   $32.0899   $32.09   $32.10   $32.10  
  Purchase #4 $27.64   3.232%   $28.5333   $28.53   $28.55   $28.50  
  Purchase #5 $189.55   5.487%   $199.9506   $199.95   $199.95   $200.00  
  Purchase #6 $98.48   6.726%   $105.1038   $105.10   $105.10   $105.10  
  Purchase #7 $101.83   5.779%   $107.7148   $107.71   $107.70   $107.70  
  7 purchase totals = $753.66       $795.4891   $795.48   $795.50   $795.50