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 $68.25   10.298%   $75.2784   $75.28   $75.30   $75.30  
  Purchase #2 $248.32   5.619%   $262.2731   $262.27   $262.25   $262.30  
  Purchase #3 $10.34   8.435%   $11.2122   $11.21   $11.20   $11.20  
  Purchase #4 $223.35   10.652%   $247.1412   $247.14   $247.15   $247.10  
  Purchase #5 $173.64   6.852%   $185.5378   $185.54   $185.55   $185.50  
  Purchase #6 $194.50   9.491%   $212.96   $212.96   $212.95   $213.00  
  Purchase #7 $70.79   13.196%   $80.1314   $80.13   $80.15   $80.10  
  7 purchase totals = $989.19       $1,074.5341   $1,074.53   $1,074.55   $1,074.50