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 $53.52   8.525%   $58.0826   $58.08   $58.10   $58.10  
  Purchase #2 $213.78   13.405%   $242.4372   $242.44   $242.45   $242.40  
  Purchase #3 $110.96   3.348%   $114.6749   $114.67   $114.65   $114.70  
  Purchase #4 $113.25   11.578%   $126.3621   $126.36   $126.35   $126.40  
  Purchase #5 $77.56   6.320%   $82.4618   $82.46   $82.45   $82.50  
  Purchase #6 $158.55   5.495%   $167.2623   $167.26   $167.25   $167.30  
  Purchase #7 $226.35   3.106%   $233.3804   $233.38   $233.40   $233.40  
  7 purchase totals = $953.97       $1,024.6613   $1,024.65   $1,024.65   $1,024.80