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 $81.59   5.774%   $86.301   $86.30   $86.30   $86.30  
  Purchase #2 $104.55   3.208%   $107.904   $107.90   $107.90   $107.90  
  Purchase #3 $137.47   11.842%   $153.7492   $153.75   $153.75   $153.70  
  Purchase #4 $219.27   12.167%   $245.9486   $245.95   $245.95   $245.90  
  Purchase #5 $226.25   10.641%   $250.3253   $250.33   $250.35   $250.30  
  Purchase #6 $129.32   12.464%   $145.4384   $145.44   $145.45   $145.40  
  Purchase #7 $177.64   8.453%   $192.6559   $192.66   $192.65   $192.70  
  7 purchase totals = $1,076.09       $1,182.3224   $1,182.33   $1,182.35   $1,182.20