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 $84.93   11.823%   $94.9713   $94.97   $94.95   $95.00  
  Purchase #2 $32.61   10.682%   $36.0934   $36.09   $36.10   $36.10  
  Purchase #3 $207.87   11.476%   $231.7252   $231.73   $231.75   $231.70  
  Purchase #4 $188.87   8.319%   $204.5821   $204.58   $204.60   $204.60  
  Purchase #5 $198.68   3.599%   $205.8305   $205.83   $205.85   $205.80  
  Purchase #6 $208.35   11.153%   $231.5873   $231.59   $231.60   $231.60  
  Purchase #7 $73.66   10.736%   $81.5681   $81.57   $81.55   $81.60  
  7 purchase totals = $994.97       $1,086.3579   $1,086.36   $1,086.40   $1,086.40