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 $84.74   12.735%   $95.5316   $95.53   $95.55   $95.50  
  Purchase #2 $163.47   8.581%   $177.4974   $177.50   $177.50   $177.50  
  Purchase #3 $135.40   9.455%   $148.2021   $148.20   $148.20   $148.20  
  Purchase #4 $206.61   3.662%   $214.1761   $214.18   $214.20   $214.20  
  Purchase #5 $144.57   10.873%   $160.2891   $160.29   $160.30   $160.30  
  Purchase #6 $39.42   13.433%   $44.7153   $44.72   $44.70   $44.70  
  Purchase #7 $14.94   7.662%   $16.0847   $16.08   $16.10   $16.10  
  7 purchase totals = $789.15       $856.4963   $856.50   $856.55   $856.50