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 $184.27   11.223%   $204.9506   $204.95   $204.95   $205.00  
  Purchase #2 $163.57   9.370%   $178.8965   $178.90   $178.90   $178.90  
  Purchase #3 $138.29   7.432%   $148.5677   $148.57   $148.55   $148.60  
  Purchase #4 $124.97   4.533%   $130.6349   $130.63   $130.65   $130.60  
  Purchase #5 $198.82   9.448%   $217.6045   $217.60   $217.60   $217.60  
  Purchase #6 $38.44   7.356%   $41.2676   $41.27   $41.25   $41.30  
  Purchase #7 $97.55   4.850%   $102.2812   $102.28   $102.30   $102.30  
  7 purchase totals = $945.91       $1,024.2030   $1,024.20   $1,024.20   $1,024.30