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 $90.66   5.367%   $95.5257   $95.53   $95.55   $95.50  
  Purchase #2 $198.31   3.382%   $205.0168   $205.02   $205.00   $205.00  
  Purchase #3 $230.60   5.678%   $243.6935   $243.69   $243.70   $243.70  
  Purchase #4 $192.91   6.451%   $205.3546   $205.35   $205.35   $205.40  
  Purchase #5 $136.74   11.626%   $152.6374   $152.64   $152.65   $152.60  
  Purchase #6 $214.81   5.479%   $226.5794   $226.58   $226.60   $226.60  
  Purchase #7 $40.99   4.504%   $42.8362   $42.84   $42.85   $42.80  
  7 purchase totals = $1,105.02       $1,171.6436   $1,171.65   $1,171.70   $1,171.60