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 $214.39   5.698%   $226.6059   $226.61   $226.60   $226.60  
  Purchase #2 $197.85   10.797%   $219.2119   $219.21   $219.20   $219.20  
  Purchase #3 $152.45   12.866%   $172.0642   $172.06   $172.05   $172.10  
  Purchase #4 $164.53   12.296%   $184.7606   $184.76   $184.75   $184.80  
  Purchase #5 $138.87   11.120%   $154.3123   $154.31   $154.30   $154.30  
  Purchase #6 $31.80   6.247%   $33.7865   $33.79   $33.80   $33.80  
  Purchase #7 $104.79   6.338%   $111.4316   $111.43   $111.45   $111.40  
  7 purchase totals = $1,004.68       $1,102.1730   $1,102.17   $1,102.15   $1,102.20