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 $61.49   11.629%   $68.6407   $68.64   $68.65   $68.60  
  Purchase #2 $185.87   3.238%   $191.8885   $191.89   $191.90   $191.90  
  Purchase #3 $150.44   3.182%   $155.227   $155.23   $155.25   $155.20  
  Purchase #4 $142.68   10.135%   $157.1406   $157.14   $157.15   $157.10  
  Purchase #5 $173.33   11.396%   $193.0827   $193.08   $193.10   $193.10  
  Purchase #6 $160.48   3.683%   $166.3905   $166.39   $166.40   $166.40  
  Purchase #7 $177.56   9.492%   $194.414   $194.41   $194.40   $194.40  
  7 purchase totals = $1,051.85       $1,126.7840   $1,126.78   $1,126.85   $1,126.70