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 $184.95   9.246%   $202.0505   $202.05   $202.05   $202.10  
  Purchase #2 $127.25   3.362%   $131.5281   $131.53   $131.55   $131.50  
  Purchase #3 $226.98   6.465%   $241.6543   $241.65   $241.65   $241.70  
  Purchase #4 $109.68   3.806%   $113.8544   $113.85   $113.85   $113.90  
  Purchase #5 $87.28   6.182%   $92.6756   $92.68   $92.70   $92.70  
  Purchase #6 $181.46   9.338%   $198.4047   $198.40   $198.40   $198.40  
  Purchase #7 $166.78   10.674%   $184.5821   $184.58   $184.60   $184.60  
  7 purchase totals = $1,084.38       $1,164.7497   $1,164.74   $1,164.80   $1,164.90