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 $198.62   6.373%   $211.2781   $211.28   $211.30   $211.30  
  Purchase #2 $49.25   8.278%   $53.3269   $53.33   $53.35   $53.30  
  Purchase #3 $164.65   5.488%   $173.686   $173.69   $173.70   $173.70  
  Purchase #4 $210.40   7.523%   $226.2284   $226.23   $226.25   $226.20  
  Purchase #5 $187.79   9.417%   $205.4742   $205.47   $205.45   $205.50  
  Purchase #6 $184.53   7.285%   $197.973   $197.97   $197.95   $198.00  
  Purchase #7 $103.91   4.194%   $108.268   $108.27   $108.25   $108.30  
  7 purchase totals = $1,099.15       $1,176.2346   $1,176.24   $1,176.25   $1,176.30