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 $91.82   5.401%   $96.7792   $96.78   $96.80   $96.80  
  Purchase #2 $139.82   10.520%   $154.5291   $154.53   $154.55   $154.50  
  Purchase #3 $232.95   8.528%   $252.816   $252.82   $252.80   $252.80  
  Purchase #4 $124.84   12.873%   $140.9107   $140.91   $140.90   $140.90  
  Purchase #5 $93.90   3.130%   $96.8391   $96.84   $96.85   $96.80  
  Purchase #6 $198.25   11.671%   $221.3878   $221.39   $221.40   $221.40  
  Purchase #7 $195.82   8.175%   $211.8283   $211.83   $211.85   $211.80  
  7 purchase totals = $1,077.40       $1,175.0902   $1,175.10   $1,175.15   $1,175.00