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 $177.96   13.227%   $201.4988   $201.50   $201.50   $201.50  
  Purchase #2 $126.57   12.113%   $141.9014   $141.90   $141.90   $141.90  
  Purchase #3 $27.38   8.857%   $29.805   $29.81   $29.80   $29.80  
  Purchase #4 $176.65   4.182%   $184.0375   $184.04   $184.05   $184.00  
  Purchase #5 $197.38   8.429%   $214.0172   $214.02   $214.00   $214.00  
  Purchase #6 $56.68   5.401%   $59.7413   $59.74   $59.75   $59.70  
  Purchase #7 $210.33   11.169%   $233.8218   $233.82   $233.80   $233.80  
  7 purchase totals = $972.95       $1,064.8230   $1,064.83   $1,064.80   $1,064.70