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 $113.59   5.292%   $119.6012   $119.60   $119.60   $119.60  
  Purchase #2 $212.84   4.480%   $222.3752   $222.38   $222.40   $222.40  
  Purchase #3 $118.27   6.820%   $126.336   $126.34   $126.35   $126.30  
  Purchase #4 $63.52   11.484%   $70.8146   $70.81   $70.80   $70.80  
  Purchase #5 $23.58   3.498%   $24.4048   $24.40   $24.40   $24.40  
  Purchase #6 $148.46   8.330%   $160.8267   $160.83   $160.85   $160.80  
  Purchase #7 $11.41   4.359%   $11.9074   $11.91   $11.90   $11.90  
  7 purchase totals = $691.67       $736.2659   $736.27   $736.30   $736.20