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 $212.60   9.561%   $232.9267   $232.93   $232.95   $232.90  
  Purchase #2 $69.39   7.617%   $74.6754   $74.68   $74.70   $74.70  
  Purchase #3 $106.48   11.336%   $118.5506   $118.55   $118.55   $118.60  
  Purchase #4 $208.78   7.457%   $224.3487   $224.35   $224.35   $224.30  
  Purchase #5 $151.37   5.793%   $160.1389   $160.14   $160.15   $160.10  
  Purchase #6 $177.43   10.840%   $196.6634   $196.66   $196.65   $196.70  
  Purchase #7 $173.90   12.242%   $195.1888   $195.19   $195.20   $195.20  
  7 purchase totals = $1,099.95       $1,202.4925   $1,202.50   $1,202.55   $1,202.50