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 $215.93   7.313%   $231.721   $231.72   $231.70   $231.70  
  Purchase #2 $171.27   3.201%   $176.7524   $176.75   $176.75   $176.80  
  Purchase #3 $114.85   12.530%   $129.2407   $129.24   $129.25   $129.20  
  Purchase #4 $30.77   3.585%   $31.8731   $31.87   $31.85   $31.90  
  Purchase #5 $184.50   12.697%   $207.926   $207.93   $207.95   $207.90  
  Purchase #6 $44.39   7.575%   $47.7525   $47.75   $47.75   $47.80  
  Purchase #7 $186.44   12.253%   $209.2845   $209.28   $209.30   $209.30  
  7 purchase totals = $948.15       $1,034.5502   $1,034.54   $1,034.55   $1,034.60