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 $87.59   9.665%   $96.0556   $96.06   $96.05   $96.10  
  Purchase #2 $60.27   3.184%   $62.189   $62.19   $62.20   $62.20  
  Purchase #3 $179.67   3.327%   $185.6476   $185.65   $185.65   $185.60  
  Purchase #4 $238.52   9.216%   $260.502   $260.50   $260.50   $260.50  
  Purchase #5 $239.74   5.499%   $252.9233   $252.92   $252.90   $252.90  
  Purchase #6 $124.76   3.161%   $128.7037   $128.70   $128.70   $128.70  
  Purchase #7 $178.65   8.643%   $194.0907   $194.09   $194.10   $194.10  
  7 purchase totals = $1,109.20       $1,180.1119   $1,180.11   $1,180.10   $1,180.10