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 $136.58   7.453%   $146.7593   $146.76   $146.75   $146.80  
  Purchase #2 $205.59   13.621%   $233.5934   $233.59   $233.60   $233.60  
  Purchase #3 $80.82   7.613%   $86.9728   $86.97   $86.95   $87.00  
  Purchase #4 $200.57   5.263%   $211.126   $211.13   $211.15   $211.10  
  Purchase #5 $199.54   13.323%   $226.1247   $226.12   $226.10   $226.10  
  Purchase #6 $205.51   9.871%   $225.7959   $225.80   $225.80   $225.80  
  Purchase #7 $36.83   12.776%   $41.5354   $41.54   $41.55   $41.50  
  7 purchase totals = $1,065.44       $1,171.9075   $1,171.91   $1,171.90   $1,171.90