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 $182.58   3.117%   $188.271   $188.27   $188.25   $188.30  
  Purchase #2 $105.95   9.681%   $116.207   $116.21   $116.20   $116.20  
  Purchase #3 $164.41   4.400%   $171.644   $171.64   $171.65   $171.60  
  Purchase #4 $151.60   5.301%   $159.6363   $159.64   $159.65   $159.60  
  Purchase #5 $139.69   11.310%   $155.4889   $155.49   $155.50   $155.50  
  Purchase #6 $182.48   12.555%   $205.3904   $205.39   $205.40   $205.40  
  Purchase #7 $33.91   8.198%   $36.6899   $36.69   $36.70   $36.70  
  7 purchase totals = $960.62       $1,033.3275   $1,033.33   $1,033.35   $1,033.30