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 $211.42   3.498%   $218.8155   $218.82   $218.80   $218.80  
  Purchase #2 $50.97   9.344%   $55.7326   $55.73   $55.75   $55.70  
  Purchase #3 $55.35   9.657%   $60.6951   $60.70   $60.70   $60.70  
  Purchase #4 $190.58   6.329%   $202.6418   $202.64   $202.65   $202.60  
  Purchase #5 $229.80   8.258%   $248.7769   $248.78   $248.80   $248.80  
  Purchase #6 $223.77   3.677%   $231.998   $232.00   $232.00   $232.00  
  Purchase #7 $46.59   4.154%   $48.5253   $48.53   $48.55   $48.50  
  7 purchase totals = $1,008.48       $1,067.1852   $1,067.20   $1,067.25   $1,067.10