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 $204.31   4.823%   $214.1639   $214.16   $214.15   $214.20  
  Purchase #2 $180.55   10.109%   $198.8018   $198.80   $198.80   $198.80  
  Purchase #3 $218.95   10.208%   $241.3004   $241.30   $241.30   $241.30  
  Purchase #4 $106.85   11.778%   $119.4348   $119.43   $119.45   $119.40  
  Purchase #5 $173.36   6.579%   $184.7654   $184.77   $184.75   $184.80  
  Purchase #6 $127.32   6.827%   $136.0121   $136.01   $136.00   $136.00  
  Purchase #7 $95.74   7.483%   $102.9042   $102.90   $102.90   $102.90  
  7 purchase totals = $1,107.08       $1,197.3826   $1,197.37   $1,197.35   $1,197.40