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 $228.54   7.179%   $244.9469   $244.95   $244.95   $244.90  
  Purchase #2 $166.63   11.593%   $185.9474   $185.95   $185.95   $185.90  
  Purchase #3 $86.75   5.810%   $91.7902   $91.79   $91.80   $91.80  
  Purchase #4 $148.28   3.724%   $153.8019   $153.80   $153.80   $153.80  
  Purchase #5 $115.75   5.771%   $122.4299   $122.43   $122.45   $122.40  
  Purchase #6 $233.43   12.519%   $262.6531   $262.65   $262.65   $262.70  
  Purchase #7 $62.93   9.384%   $68.8354   $68.84   $68.85   $68.80  
  7 purchase totals = $1,042.31       $1,130.4048   $1,130.41   $1,130.45   $1,130.30