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 $246.82   6.271%   $262.2981   $262.30   $262.30   $262.30  
  Purchase #2 $98.90   8.518%   $107.3243   $107.32   $107.30   $107.30  
  Purchase #3 $139.35   10.687%   $154.2423   $154.24   $154.25   $154.20  
  Purchase #4 $102.33   4.535%   $106.9707   $106.97   $106.95   $107.00  
  Purchase #5 $185.52   5.133%   $195.0427   $195.04   $195.05   $195.00  
  Purchase #6 $162.31   13.263%   $183.8372   $183.84   $183.85   $183.80  
  Purchase #7 $167.46   8.745%   $182.1044   $182.10   $182.10   $182.10  
  7 purchase totals = $1,102.69       $1,191.8197   $1,191.81   $1,191.80   $1,191.70