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 $59.85   4.733%   $62.6827   $62.68   $62.70   $62.70  
  Purchase #2 $122.46   3.519%   $126.7694   $126.77   $126.75   $126.80  
  Purchase #3 $194.87   12.169%   $218.5837   $218.58   $218.60   $218.60  
  Purchase #4 $208.35   12.813%   $235.0459   $235.05   $235.05   $235.00  
  Purchase #5 $17.58   13.302%   $19.9185   $19.92   $19.90   $19.90  
  Purchase #6 $131.81   10.152%   $145.1914   $145.19   $145.20   $145.20  
  Purchase #7 $118.75   8.548%   $128.9008   $128.90   $128.90   $128.90  
  7 purchase totals = $853.67       $937.0924   $937.09   $937.10   $937.10