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 $55.72   9.674%   $61.1104   $61.11   $61.10   $61.10  
  Purchase #2 $208.97   12.767%   $235.6492   $235.65   $235.65   $235.60  
  Purchase #3 $75.29   9.236%   $82.2438   $82.24   $82.25   $82.20  
  Purchase #4 $62.44   9.746%   $68.5254   $68.53   $68.55   $68.50  
  Purchase #5 $190.66   13.419%   $216.2447   $216.24   $216.25   $216.20  
  Purchase #6 $86.88   7.150%   $93.0919   $93.09   $93.10   $93.10  
  Purchase #7 $168.99   11.245%   $187.9929   $187.99   $188.00   $188.00  
  7 purchase totals = $848.95       $944.8583   $944.85   $944.90   $944.70