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 $181.57   10.707%   $201.0107   $201.01   $201.00   $201.00  
  Purchase #2 $180.77   9.658%   $198.2288   $198.23   $198.25   $198.20  
  Purchase #3 $161.39   12.867%   $182.1561   $182.16   $182.15   $182.20  
  Purchase #4 $177.31   7.620%   $190.821   $190.82   $190.80   $190.80  
  Purchase #5 $180.62   5.810%   $191.114   $191.11   $191.10   $191.10  
  Purchase #6 $30.90   8.461%   $33.5144   $33.51   $33.50   $33.50  
  Purchase #7 $190.83   7.292%   $204.7453   $204.75   $204.75   $204.70  
  7 purchase totals = $1,103.39       $1,201.5903   $1,201.59   $1,201.55   $1,201.50