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 $212.94   5.766%   $225.2181   $225.22   $225.20   $225.20  
  Purchase #2 $224.46   5.273%   $236.2958   $236.30   $236.30   $236.30  
  Purchase #3 $88.43   4.589%   $92.4881   $92.49   $92.50   $92.50  
  Purchase #4 $141.99   11.387%   $158.1584   $158.16   $158.15   $158.20  
  Purchase #5 $79.58   7.297%   $85.387   $85.39   $85.40   $85.40  
  Purchase #6 $34.76   3.330%   $35.9175   $35.92   $35.90   $35.90  
  Purchase #7 $206.54   5.587%   $218.0794   $218.08   $218.10   $218.10  
  7 purchase totals = $988.70       $1,051.5443   $1,051.56   $1,051.55   $1,051.60