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 $68.84   10.266%   $75.9071   $75.91   $75.90   $75.90  
  Purchase #2 $145.79   12.864%   $164.5444   $164.54   $164.55   $164.50  
  Purchase #3 $206.89   4.337%   $215.8628   $215.86   $215.85   $215.90  
  Purchase #4 $197.60   7.408%   $212.2382   $212.24   $212.25   $212.20  
  Purchase #5 $242.38   4.231%   $252.6351   $252.64   $252.65   $252.60  
  Purchase #6 $215.46   12.845%   $243.1358   $243.14   $243.15   $243.10  
  Purchase #7 $247.31   12.196%   $277.4719   $277.47   $277.45   $277.50  
  7 purchase totals = $1,324.27       $1,441.7953   $1,441.80   $1,441.80   $1,441.70