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 $213.77   4.832%   $224.0994   $224.10   $224.10   $224.10  
  Purchase #2 $232.99   10.867%   $258.309   $258.31   $258.30   $258.30  
  Purchase #3 $93.80   11.544%   $104.6283   $104.63   $104.65   $104.60  
  Purchase #4 $241.44   9.174%   $263.5897   $263.59   $263.60   $263.60  
  Purchase #5 $104.48   13.237%   $118.31   $118.31   $118.30   $118.30  
  Purchase #6 $212.63   8.351%   $230.3867   $230.39   $230.40   $230.40  
  Purchase #7 $23.98   9.858%   $26.3439   $26.34   $26.35   $26.30  
  7 purchase totals = $1,123.09       $1,225.6670   $1,225.67   $1,225.70   $1,225.60