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 $57.67   7.413%   $61.9451   $61.95   $61.95   $61.90  
  Purchase #2 $146.59   4.810%   $153.641   $153.64   $153.65   $153.60  
  Purchase #3 $23.89   11.469%   $26.6299   $26.63   $26.65   $26.60  
  Purchase #4 $94.66   4.751%   $99.1573   $99.16   $99.15   $99.20  
  Purchase #5 $203.55   5.337%   $214.4135   $214.41   $214.40   $214.40  
  Purchase #6 $203.73   3.804%   $211.4799   $211.48   $211.50   $211.50  
  Purchase #7 $59.39   6.713%   $63.3769   $63.38   $63.40   $63.40  
  7 purchase totals = $789.48       $830.6436   $830.65   $830.70   $830.60