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 $42.88   4.178%   $44.6715   $44.67   $44.65   $44.70  
  Purchase #2 $225.82   6.763%   $241.0922   $241.09   $241.10   $241.10  
  Purchase #3 $219.43   5.224%   $230.893   $230.89   $230.90   $230.90  
  Purchase #4 $250.54   4.804%   $262.5759   $262.58   $262.60   $262.60  
  Purchase #5 $154.28   3.753%   $160.0701   $160.07   $160.05   $160.10  
  Purchase #6 $25.78   3.395%   $26.6552   $26.66   $26.65   $26.70  
  Purchase #7 $95.28   10.420%   $105.2082   $105.21   $105.20   $105.20  
  7 purchase totals = $1,014.01       $1,071.1661   $1,071.17   $1,071.15   $1,071.30