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 $44.48   3.437%   $46.0088   $46.01   $46.00   $46.00  
  Purchase #2 $208.82   8.402%   $226.3651   $226.37   $226.35   $226.40  
  Purchase #3 $242.35   13.161%   $274.2457   $274.25   $274.25   $274.20  
  Purchase #4 $174.93   5.279%   $184.1646   $184.16   $184.15   $184.20  
  Purchase #5 $99.55   4.556%   $104.0855   $104.09   $104.10   $104.10  
  Purchase #6 $241.36   6.139%   $256.1771   $256.18   $256.20   $256.20  
  Purchase #7 $27.28   5.536%   $28.7902   $28.79   $28.80   $28.80  
  7 purchase totals = $1,038.77       $1,119.8370   $1,119.85   $1,119.85   $1,119.90