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 $144.96   6.247%   $154.0157   $154.02   $154.00   $154.00  
  Purchase #2 $24.73   5.132%   $25.9991   $26.00   $26.00   $26.00  
  Purchase #3 $22.79   11.418%   $25.3922   $25.39   $25.40   $25.40  
  Purchase #4 $162.59   7.378%   $174.5859   $174.59   $174.60   $174.60  
  Purchase #5 $173.49   6.726%   $185.1589   $185.16   $185.15   $185.20  
  Purchase #6 $178.98   10.294%   $197.4042   $197.40   $197.40   $197.40  
  Purchase #7 $177.91   5.363%   $187.4513   $187.45   $187.45   $187.50  
  7 purchase totals = $885.45       $950.0073   $950.01   $950.00   $950.10