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 $93.47   3.239%   $96.4975   $96.50   $96.50   $96.50  
  Purchase #2 $148.56   7.602%   $159.8535   $159.85   $159.85   $159.90  
  Purchase #3 $164.34   6.835%   $175.5726   $175.57   $175.55   $175.60  
  Purchase #4 $219.70   13.150%   $248.5906   $248.59   $248.60   $248.60  
  Purchase #5 $170.74   3.717%   $177.0864   $177.09   $177.10   $177.10  
  Purchase #6 $23.29   6.710%   $24.8528   $24.85   $24.85   $24.90  
  Purchase #7 $206.46   13.137%   $233.5827   $233.58   $233.60   $233.60  
  7 purchase totals = $1,026.56       $1,116.0361   $1,116.03   $1,116.05   $1,116.20